Task: Question Answering
Input (English): Problem: ram, who is half as efficient as krish, will take 21 days to complete a task if he worked alone. if ram and krish worked together, how long will they take to complete the task ?
Options: a. 16 days, b. 12 days, c. 8 days, d. 7 days, e. 18 days
Output (English): d