A can do a piece of work in 20 days and B can do it in 30 days and C can do it 10 days. They started the work together and A leaves after 2 days and C leaves after 4 days from the beginning. How long will work lost?
Pick.
A) 13 B) 16 C) 25 D) 14 E) 15

Rationale: 2 / 20 + x / 30 + 4 / 10 = 1 x = 300 / 20 = 15 answer : e
Answer: E