A compound (C4H6O2) has a strong band in the infrared at 1760 cm^-1. Its 13C NMR spectrum exhibits signals at 8 20.2 (CH3), 96.8 (CH2), 141.8 (CA), and 167.6 (C). The 1H NMR spectrum of the compound has a three-proton singlet at δ 2.1 along with three other signals, each of which is a doublet of doublets, at 8 4.7, 4.9, and 7.3. What is the structure of the compound?