A and B together can complete a work in 12 days. A alone can complete it in 20 days. If B does the work only for half a day daily, then in how many days A and B together will complete the work?	Choose the correct choice from the following choices:
A) 11 days	B) 77 days	C) 15 days	D) 18 days	E) 19 days
B's 1 day work = (1/12 - 1/20) = 1/30   Now, (A + B)'s 1 day work = (1/20 + 1/60) = 1/15   So, A and B together will complete the work in 15 days.   Answer:15 days
<result>C</result>
A and B together can complete a work in 12 days. A alone can complete it in 20 days. If B does the work only for half a day daily, then in how many days A and B together will complete the work?