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

Example Input: Problem: how many kilograms of pure water is to be added to 100 kilograms of a 30 % saline solution to make it a 10 % saline solution . 
Options: a ) 100 , b ) 200 , c ) 300 , d ) 400 , e ) 500
Example Output: b

Example Input: Problem: the ratio between the current age of a and b is 6 : 7 . if b is 4 years old than a . what will be the ratio of the ages of a and b after 4 years ? 
Options: a ) 7 : 8 , b ) 8 : 9 , c ) 4 : 6 , d ) 4 : 8 , e ) 5 : 8
Example Output: a

Example Input: Problem: in a class of 87 students 41 are taking french , 22 are taking german . of the students taking french or german , 9 are taking both courses . how many students are not enrolled in either course ? 
Options: a ) 6 , b ) 15 , c ) 24 , d ) 33 , e ) 54
Example Output:
d