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

Example Input: Problem: in what ratio must tea at rs . 64 per kg be mixed with tea at rs . 74 per kg so that the mixture must be worth rs . 69 per kg ? 
Options: a ) 1 : 1 , b ) 3 : 2 , c ) 4 : 3 , d ) 5 : 3 , e ) none
Example Output: a

Example Input: Problem: the ratio of the arithmetic mean of two numbers to one of the numbers is 5 : 9 . what is the ratio of the smaller number to the larger number ? 
Options: a ) 1 : 5 , b ) 1 : 6 , c ) 1 : 7 , d ) 1 : 8 , e ) 1 : 9
Example Output: e

Example Input: Problem: sandy is younger than molly by 16 years . if the ratio of their ages is 7 : 9 , how old is sandy ? 
Options: a ) 42 , b ) 49 , c ) 56 , d ) 63 , e ) 70
Example Output:
c