Compute each part of given problem:
Problem: A spaceship is moving at a speed ot 0.9c away from an observer at rest. A boy in the spaceship shoots a proton gun with protons having a speed of 0.6c.
Part A: What is the speed of the protons measured by the observer at rest when the gun is shot away from the observer?
Part B: What is the speed of the protons measured by the observer at rest when the gun is shot toward the observer?
Please show work on how to solve all parts of given problem!