Kathleen can paint a room in 2 hours, and Anthony can paint an identical room in 7 hours. How many hours would it take Kathleen and Anthony to paint both rooms if they work together at their respective rates?  Choose the correct choice from the following answers.
A) 28 / 9  B) 4 / 3  C) 15 / 8  D) 9 / 4  E) 15 / 4

Rationale: ( 1 / 2 + 1 / 7 ) t = 2 t = 28 / 9 answer : a
Answer: A