I don't think your answer to problem "a" is correct regarding the observed closing speed by someone at point "c". There is no constraint against 2 objects approaching each other with a closing velocity >c because neither object is moving faster than c relative to the stationary observer.
The transformation you used only applies to the observers who are moving relative to each other so that their velocities relative to each other are always <c.
I don't think your answer to problem "a" is correct regarding the observed closing speed by someone at point "c". There is no constraint against 2 objects approaching each other with a closing velocity >c because neither object is moving faster than c relative to the stationary observer.
The transformation you used only applies to the observers who are moving relative to each other so that their velocities relative to each other are always <c.
deedubya286 1 month ago