Task: Question Answering
Input (English): Problem: a, b and c can do a piece of work in 24 days, 30 days and 40 days respectively. they began the work together but c left 12 days before the completion of the work. in how many days was the work completed ?
Options: a. 13 days, b. 16 days, c. 18 days, d. 11 days, e. 38 days
Output (English): a