\[\boxed{\mathbf{290.}}\]
\[Всего\ карандашей:\]
\[20 + 16 = 36.\]
\[\textbf{а)}\ \frac{C}{N} = \frac{20}{36} = \frac{5}{9}.\]
\[\textbf{б)}\ \frac{K}{N} = \frac{16}{36} = \frac{4}{9}.\]