Compounds A and B are isomeric diketones of molecular formula C6H10O2. The 1H NMR spectrum of compound A contains two signals, both singlets, at 2.2

Compounds A and B are isomeric diketones of molecular formula C6H10O2. The 1H NMR spectrum of compound A contains two signals, both singlets, at δ 2.2 (6 protons) and 2.8 ppm (4 protons). The 1H NMR spectrum of compound B contains two signals, one at δ 1.3 ppm (triplet, 6 protons) and the other at δ 2.8 ppm (quartet, 4 protons). What are the structures of compounds A and B?