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: in a river flowing at 2 km / hr , a boat travels 40 km upstream and then returns downstream to the starting point . if its speed in still water be 6 km / hr , find the total journey time . 
Options: a ) 10 hours , b ) 12 hours , c ) 14 hours , d ) 15 hours , e ) none of these
Example Output: d

Example Input: Problem: a & b started a partnership business . a ' s investment was thrice the investment of b and the period of his investment was two times the period of investments of b . if b received rs 5000 as profit , what is their total profit ? 
Options: a ) 28000 , b ) 30000 , c ) 32000 , d ) 35000 , e ) none of these
Example Output: d

Example Input: Problem: a student got twice as many sums wrong as he got right . if he attempted 54 sums in all , how many did he solve correctly ? 
Options: a ) 12 , b ) 16 , c ) 18 , d ) 24 , e ) 26
Example Output:
c