Task: Question Answering
Input (English): Problem: a can do a piece of work in 15 days. a does the work for 5 days only and leaves the job. b does the remaining work in 6 days. in how many days b alone can do the work ?
Options: a. 5 days, b. 7 days, c. 12 days, d. 9 days, e. 10 days
Output (English): d