USAAAO — 2015 Practice Round

In a distant solar system, two planets, A and B, orbit a central main sequence star, like our sun. A day on Planet A lasts 20 Earth hours, and there are 240 such days in a year on Planet A. Likewise, a day on Planet B lasts 38 hours, and there are 220 such days in a year on Planet B. What is the synodic period with respect to these two planets, in Earth years?