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'.

Ex Input:
Problem: ( 51 + 52 + 53 + + 100 ) is equal to :
Options: a ) 2525 , b ) 2975 , c ) 3225 , d ) 3775 , e ) 3885

Ex Output:
d

Ex Input:
Problem: a envelop weight 8.5 gm , if 820 of these envelop are sent with an advertisement mail . how much wieght ?
Options: a ) 6.6 kg , b ) 6.8 kg , c ) 6.7 kg , d ) 6.97 kg , e ) 7.8 kg

Ex Output:
d

Ex Input:
Problem: mary is expected to pay back a total sum of $ 819200 to her bank as mortgage . if she is expected to make a payment which is double of the previous months amount , how long will it take her to fully repay the loan if her initial payment was $ 400 .
Options: a ) 13 , b ) 15 , c ) 12 , d ) 10 , e ) 11

Ex Output:
e