           
                                                 
                                                                                                   
       
            
   
     1917                                                                                                                                                                                     
     15       50                                                                      80       40              270     150     5000     1960                  2000              
                                                                                                                                                                                  
1                          
2              
3                                
4                                          
      
                    
        
                                                    

  
                                                                                                                                                   
                                                                                                                                                                                  
        
                                                                                                                                                                                
                                                                                                                                       
        
                       8                                                                                                                                                                                                                                                                      
        
                                    
                     
                                                                                                                                                                                                                                                        
                                                                 
          
         1985 1 15   
                