Task: Question Answering
Input (English): Problem: joe invested a certain sum of money in a simple interest bond whose value grew to $ 310 at the end of 3 years and to $ 410 at the end of another 5 years. what was the rate of interest in which he invested his sum ?
Options: a. 6 %, b. 7 %, c. 8 %, d. 9 %, e. 10 %
Output (English): c