Task: Question Answering
Input (English): Problem: if it would take one machine 20 minutes to fill a large production order and another machine 30 minutes to fill the same order, how many minutes would it take both machines working together, at their respective rates, to fill the order ?
Options: a. 10 min, b. 12 min, c. 15 min, d. 20 min, e. 18 min
Output (English): b