Kathleen can paint a room in 2 hours, and Anthony can paint an identical room in 5 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 option:
A) 20 / 7
B) 4 / 3
C) 15 / 8
D) 9 / 4
E) 15 / 4

Rationale: "( 1 / 2 + 1 / 5 ) t = 2 t = 20 / 7 answer : a"
Answer: A