When a Yom Tov falls on Friday, a person may not cook on Yom Tov primarily for the Sabbath, but he may cook for Yom Tov, and if anything is left over, it may be left for the Sabbath. But one should prepare a dish prior to Yom Tov and depend on it for the Sabbath. Beis Shammai say: Two dishes. But Beis Hillel say: One dish. Yet they agree concerning a fish and the egg on it, because they are two dishes. If one ate it or it was lost, one may not depend on it to cook primarily [for the Sabbath]. But if he left any of it over, he may depend on it [to cook] for the Sabbath.