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

Ex Input:
Problem: in what ratio should a 20 % methyl alcohol solution be mixed with a 50 % methyl alcohol solution so that the resultant solution has 40 % methyl alcohol in it ? 
Options: a ) 1 : 3 , b ) 1 : 2 , c ) 2 : 3 , d ) 2 : 1 , e ) 3 : 1

Ex Output:
b


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: how many of the positive factors of 24 are not factors of 25 
Options: a ) 2 , b ) 3 , c ) 4 , d ) 1 , e ) 5

Ex Output:

d