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