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

Example Input: Problem: a can contains a mixture of liquids a and b is the ratio 7 : 5 . when 3 litres of mixture are drawn off and the can is filled with b , the ratio of a and b becomes 7 : 9 . how many liter of liquid a was contained by the can initially ? 
Options: a ) 7 , b ) 10 , c ) 12 , d ) 14 , e ) 16
Example Output: a

Example Input: Problem: if m = 3 ^ n , what is the greatest value of n for which m is a factor of 19 ! 
Options: a ) 8 , b ) 10 , c ) 12 , d ) 14 , e ) 16
Example Output: a

Example Input: Problem: the ratio of three numbers is 5 : 1 : 4 and their sum is 1000 . the last number of the three numbers is ? 
Options: a ) 24 , b ) 26 , c ) 27 , d ) 400 , e ) 30
Example Output:
d