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: village x has a population of 76000 , which is decreasing at the rate of 1200 per year . village y has a population of 42000 , which is increasing at the rate of 800 per year . in how many years will the population of the two villages be equal ?
Options: a ) 15 , b ) 17 , c ) 11 , d ) 18 , e ) 13
Example Output: b

Example Input: Problem: if the price of a tv is first decreased by 10 % and then increased by 30 % , then the net change in the price will be :
Options: a ) 4 % increase , b ) 17 % increase , c ) 10 % decrease , d ) 6 % increase , e ) none of these
Example Output:
b