A and B can complete a work in 15days and 10day. They started doing the work together but after 2days B had to leave and A alone completed the remaining work. The whole work was completed in?
Choose the correct choice from the following answers
A) 10 days B) 12 days C) 15 days D) 8 days E) 16 days

Rationale: "a + b 1 day work = 1 / 15 + 1 / 10 = 1 / 6 work done by a and b in 2 days = 1 / 6 * 2 = 1 / 3 remaining work = 1 - 1 / 3 = 2 / 3 now 1 / 15 work is done by a in 1 day 2 / 3 work will be done by a in 15 * 2 / 3 = 10 days total time taken = 10 + 2 = 12 days answer is b"
Answer: B