Task: Question Answering
Input (English): Problem: a can do a piece of work in 4 days. b can do it in 7 days. with the assistance of c they completed the work in 2 days. find in how many days can c alone do it ?
Options: a. 22 days, b. 28 / 3 days, c. 67 days, d. 17 / 5 days, e. 18 days
Output (English): b