Task: Question Answering
Input (English): Problem: a, b, c can complete a piece of work in 3,9 and 15 days respectively. working together, they will complete the same work in how many days ?
Options: a. 45 / 23, b. 55 / 23, c. 61 / 57, d. 12 / 13, e. 22 / 23
Output (English): a