A can do a piece of work in 10 days and B in 20 days. They began the work together but 5 days before the completion of the work, A leaves. The work was completed in?
Choose the correct choice from the following answers
A) 15 days	B) 10 days	C) 12 days	D) 19 days	E) 13 days

Rationale: b ( x â € “ 5 ) / 10 + x / 20 = 1 x = 10 days
Answer: B