1. Rocket A leaves a space station with a speed of 0.54 c. Later, rocket B leaves in the same direction  with a speed of 0.85 c. What is the velocity of rocket A as observed from rocket B?

2.  Global positioning satellites (GPS) work by sending out signals with their current location and  time. When your device on Earth gets signals from multiple satellites it can tell by the time that they
each report which signals took the longest to reach you. For this to work the satellites need very  accurate clocks. They are moving at roughly 14,000 km/hr relative to the Earth, though, so they need
to consider the effect of time dilation. How much time does a GPS satellite lose each day relative to a  clock on Earth?