Task: Question Answering
Input (English): Problem: joan took out a mortgage from hel local bank. each monthly mortgage payment she makes must be triple the amount of the previous month ' s payment. if her first payment is $ 100, and the total amount she must pay back is $ 914800, how many months will it take joan to pay back her mortgage ?
Options: a. 6, b. 8, c. 10, d. 9, e. 13
Output (English): d