16.5, 17.5,18         
            
 
            
 
            
16, 18, 19         
            
 
            
 
            
 
            
 
            
 
            
 
            
 
            
 
            
 
            
 
            
 
            
 
            
 
            
 
            
 
            
 
            
 
            
 
            
 
            
 
            
 
            
 
            
 
            
 
            
 
            
 
            
 
            
 
            
 
            
 
            
 
            
 
            
 
            
17         
            
 
            
 
            
 
            
 
            
 
            
 
            
 
            
 
            
 
            
17         
            
16, 17, 18