Calculate the degree of unsaturation in each of the following formulas:
(a) $\mathrm{C}_{6} \mathrm{H}_{5} \mathrm{N}$
(b) $\mathrm{C}_{6 \mathrm{H}_{5} \mathrm{NO}_{2}}$
(c) $\mathrm{C}_{8} \mathrm{H}_{9} \mathrm{Cl}_{3}$
(d) $\mathrm{C}_{9} \mathrm{H}_{16} \mathrm{Br}_{2}$
$\mathrm{C}_{10} \mathrm{H}_{12} \mathrm{N}_{2} \mathrm{O}_{3}$
(f) $\mathrm{C}_{20} \mathrm{H}_{32} \mathrm{CIN}$