A 0.8715 g sample of sorbic acid, a compound first obtained from the berries of a certain ash tree, is burned completely in oxygen to give 2.053 g of carbon dioxide and 0.5601 g of water. The empirical formula of sorbic acid is
◦ CH2O
◦ C3H4O
◦ CH4O3
◦ C3H4O2
◦ C2H4O2