3. An observer in frame S' is moving to the right (+x-direction) at speed u = 0.850c away from a stationary observer in frame S. The observer in S' measures the speed v' of a particle moving to the right away from her. What speed v does the observer in S measure for the particle if (a) v'= 0.990c (b) v' = 0.900c (c) v'=0.750c