Suzanne observes two light pulses to be emitted from the same location, but separated in time by

Question:

Suzanne observes two light pulses to be emitted from the same location, but separated in time by 3.00 μs. Mark sees the emission of the same two pulses separated in time by 9.00 μs.
(a) How fast is Mark moving relative to Suzanne?
(b) According to Mark, what is the separation in space of the two pulses?