Calculate the degree of unsaturation in each of the following formulas:
(a) Cholesterol, $\mathrm{C}_{27} \mathrm{H}_{46} \mathrm{O}$
(b) DDT, $\mathrm{C}_{14} \mathrm{H}_9 \mathrm{Cl}_5$
(c) Prostaglandin $\mathrm{E}_1, \mathrm{C}_{20} \mathrm{H}_{34} \mathrm{O}_5$
(d) Caffeine, $\mathrm{C}_8 \mathrm{H}_{10} \mathrm{~N}_4 \mathrm{O}_2$
(e) Cortisone, $\mathrm{C}_{21} \mathrm{H}_{28} \mathrm{O}_5$
(f) Atropine, $\mathrm{C}_{17} \mathrm{H}_{23} \mathrm{NO}_3$