On their 20th birthday, twins Ann and Nancy receive a gift spaceship from their grandfather. While Nancy remains on Earth, Ann pilots her ship, "Dreamboat Annie", toward the 25-ly distant Klaatu nebula at 3/4 light speed. Once she arrives, Ann spends 2 years exploring the nebula and visiting distant relatives. After her visit, in a hurry to get back home and see her sister Ann propels her spaceship to 99% light speed on her journey back to Earth. How old is Ann when she returns to Earth? How old is her twin sister, Nancy?