Task: Question Answering
Input (English): Problem: a sum of money becomes 7 / 6 of itself in 7 years at a certain rate of simple interest. the rate per annum is ?
Options: a. 50 / 13, b. 50 / 17, c. 50 / 19, d. 50 / 21, e. 50 / 23
Output (English): d