In this task, you need to answer the given multiple-choice question on the general math. Classify your answers into 'a', 'b', 'c', 'd', and 'e'.

Example Input: Problem: if a - b = 5 and a 2 + b 2 = 31 , find the value of ab . 
Options: a ) 9 , b ) 2 , c ) 3 , d ) 7 , e ) 12
Example Output: c

Example Input: Problem: in a group of ducks and cows , the total number of legs are 22 more than twice the no . of heads . find the total no . of buffaloes . 
Options: a ) 11 , b ) 12 , c ) 13 , d ) 15 , e ) 16
Example Output: a

Example Input: Problem: a bus started its journey from chennai and reached mumbai in 50 min with its average speed of 60 km / hr . if the average speed of the bus is increased by 6 km / hr , how much time will it take to cover the same distance ? 
Options: a ) 45 min . , b ) 55 min . , c ) 65 min . , d ) 60 min . , e ) 50 min .
Example Output:
b