Two compounds with the molecular formula C₅H₁₀O have the following ¹H and ¹³CNMR data. Both compounds have a strong IR absorption band in the 1710–1740 cm−1 region. Elucidate the structure of these two compounds and interpret the spectra. Make a sketch of each NMR spectrum.

(a) 1H NMR: δ 2.55 (septet, 1H), 2.10 (s, 3H), 1.05 (d, 6H) ¹³C NMR: δ 212.6, 41.5, 27.2, 17.8

(b) 1H NMR: δ 2.38 (t, 2H), 2.10 (s, 3H), 1.57 (sextet, 2H), 0.88 (t, 3H) ¹³C NMR: δ 209.0, 45.5, 29.5, 17.0, 13.2