Task: Question Answering
Input (English): Problem: a can do a work in 15 days and b in 20 days. if they work on it together for 5 days, then the fraction of the work that is left is
Options: a. 8 / 17, b. 7 / 15, c. 3 / 15, d. 5 / 12, e. 1 / 4
Output (English): d