(3-6)  Cormorant has a rest mass of 2.5 kg. If you are stationary on the beach and he is flying past at 2 ms-1, calculate his mass in your frame of reference. Now suppose that he works out a lot and manages to boost his peak flying speed to 2.95 x 108 ms-1 (around 98% of the speed of light). What happens to his mass now?