At a rocket speed V = 0.5 s relative to the Earth, its mass for an observer on the rocket will

At a rocket speed V = 0.5 s relative to the Earth, its mass for an observer on the rocket will be equal to M = 200 tons. What is the mass of a stationary rocket?

These tasks: V (the speed of the rocket under consideration relative to the Earth) = 0.5C; m (the mass of the rocket for an observer on it) = 200 tons.

Since the frame of reference is connected with the Earth, it will seem to the observer on the rocket that it is motionless and the apparent mass of the rocket is precisely the rest mass.

Answer: The mass of a stationary rocket is 200 tons.