Worker A takes 12 hours to do a job. Worker B takes 15 hours to do the same job. How long it take both A & B, working together but independently, to do the same job?	Choose the correct choice from the following
A) 40 days	B) 40 / 9 days	C) 39 / 9 days	D) 30 / 9 days	E) 20 / 3 days

Rationale: "a ' s one hour work = 1 / 12 . b ' s one hour work = 1 / 15 . ( a + b ) ' s one hour work = 1 / 12 + 1 / 15 = 9 / 60 = 3 / 20 . both a & b can finish the work in 20 / 3 days e"
Answer: E