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: find the principle on a certain sum of money at 5 % per annum for 3 1 / 5 years if the amount being rs . 580 ?
Options: a ) rs . 500 , b ) rs . 5100 , c ) rs . 530 , d ) rs . 540 , e ) none of these
Example Output: a

Example Input: Problem: ages of two sisters differ by 9 years . if 5 years ago , the elder one was twice as old the younger one , find their present age
Options: a ) 1228 , b ) 1423 , c ) 1632 , d ) 1834 , e ) 1932
Example Output: b

Example Input: Problem: what is the sum of all possible solutions to the equation 2 x ^ 2 x 9 = x + 1 ?
Options: a ) - 2 , b ) 2 , c ) 3 , d ) 5 , e ) 6
Example Output:
d