In Figure a, particle P is to move parallel to the x and x axes of reference frames S and S', at a certain velocity relative to frame S. Frame S' is to move parallel to the r axis of frame S at velocity v. Figure b gives the velocity u' of the particle relative to frame S' for a range of values for y. The vertical axis scale is set by u_a = – 0.800c. What value will u' have if? 

(a) v = 0.80c and 

(b) v → c?