According to Anna, on Earth, Bob is on a spaceship moving at 0.8c towards Earth, and Carl, a little farther out, is on a spaceship moving a 0.9c towards Earth. According to Bob, how fast is Carl moving relative to Earth?

Question

(a) According to Bob, how fast and in what direction is Carl moving relative to himself (Bob)?
--- I solved part a and got 0.357c and used u' = u-v divide by 1-uv/c^2.

But I confused about part b above.