Task: Question Answering
Input (English): Problem: a and b together can complete a work in 12 days. a alone complete it in 20 days. if b does the work only for half a day daily, then in how many days a and b together will complete the work ?
Options: a. 110 days, b. 11 days, c. 15 days, d. 20 days, e. 17 days
Output (English): c