Consider the situation as depicted in Question 7.6. Whose clock (his, yours, or A's) does B observe to run slowest? Whose clock does A observe to run slowest? If all three ships have the same length when measured in their own rest frames, which ship does B observe to be shortest? If spaceship A sends out a pulse of red light, will B see it to be blueshifted or redshifted?
(7.6) Two spaceships (A and B) approach you at 9/10ths the speed of light (0.9c) from opposite directions. They send out radio messages. What is the speed you measure for the radio waves from A and B? What is the speed of the radio waves from A as measured by B? What speed does B measure for your motion? How fast does spaceship B observe spaceship A to be moving?