Task: Question Answering
Input (English): Problem: a and b can do a work in 5 days and 10 days respectively. a starts the work and b joins him after 4 days. in how many days can they complete the remaining work ?
Options: a. 6 days, b. 2 / 3 days, c. 8 days, d. 3 days, e. 9 days
Output (English): b