In this task, you need to provide the correct option for a given problem from the provided options.

Ex Input:
Problem: solution a is 20 % salt and solution b is 70 % salt . if you have 30 ounces of solution a and 60 ounces of solution b , in what ratio could you mix solution a with solution b to produce 50 ounces of a 50 % salt solution ? 
Options: a ) 6 : 4 , b ) 6 : 14 , c ) 2 : 3 , d ) 4 : 6 , e ) 3 : 7

Ex Output:
c


Ex Input:
Problem: at the faculty of aerospace engineering , 312 students study random - processing methods , 232 students study scramjet rocket engines and 112 students study them both . if every student in the faculty has to study one of the two subjects , how many students are there in the faculty of aerospace engineering ? 
Options: a ) 424 . , b ) 428 . , c ) 430 . , d ) 432 . , e ) 436

Ex Output:
d


Ex Input:
Problem: find the compound ratio of ( 4 : 3 ) , ( 1 : 3 ) and ( 2 : 3 ) is 
Options: a ) 16 : 27 , b ) 12 : 13 , c ) 13 : 14 , d ) 14 : 15 , e ) 31 : 27

Ex Output:

a