Suppose rocket traveler Amelia has a clock made on Earth. Every year on her birthday she sends a light signal to brother Casper on Earth. (a) At what rate does Casper receive the signals during Amelia's outward journey? (b) At what rate does he receive the signals during her return journey? (c) How many of Amelia's birthday signals does Casper receive during the journey that he measures to last 20 years?