An unknown with MF C_7H_12O has the following spectral data: IR: 1700 cm^-1 (strong) & 1640 cm^-1 ^1H NMR: (ppm, splitting pattern, integration value) 1.90 ppm, singlet, 3H 2.10 ppm, singlet, 3H 2.15 ppm, singlet, 3H 2.20 ppm, singlet, 3H ^13C NMR: (a) Calculate HDI: show work. (b) What bonds are present based on the IR data? Circle all that apply. (c) Indicate each type of carbon in the table above (C, CH, CH_2, or CH_3). (d) Draw the structure of this unknown. Please give only one answer in the box below.