Subject: mathqa
Question: 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 ?
Option: 
A: 15 / 4
B: 28 / 9
C: 4 / 3
D: 9 / 4
Answer: B