(20 pts) Ann and her twin brother Bob are peacefully walking when Bob is suddenly beamed-up to a passing spaceship, moving at a speed of 0.75c relative to the Earth. Six years later, Ann gets a message from Bob: "I finally overpowered my captors and gained control of the ship. On my way home!" Assume that the spaceship was turned around suddenly, and that its speed remained 0.75c in both directions