A spaceship travels at speed v (v << c) to a distant star. Upon reaching the star, it decelerates and then accelerates back up to speed v in the opposite direction (uniformly, and in a short time compared to the total journey time). By what fraction does the traveler age less than her twin on earth? (Ignore the gravity from the earth.) Work in:
(a) The earth frame.
(b) The spaceship frame.