Explanation:

 let a,b,c,d are positive integers,

(a+b+c+d)/4=72.5;

=> a+b+c+d =(72.5*4)=290;

lets consider a=117 and d=15 as given

and b-c=12 as given by substituting and a and d we get

b+c=158

by adding b-c=12, b+c=158, we get

2b=170 => b=85;

by substituting b=85 we get c=73 ;

b = 85 is the higher of b and c which is not available in the options.