Ans: (a) $\dfrac{1}{28}$ (b) $\dfrac{27}{28}$
- The required probability
$\begin{array}{cl}
= & \dfrac{C^5_4C^{11}_2+C^5_5C^{11}_1}{C^{16}_6} \\
= & \dfrac{1}{28}
\end{array}$ - The required probability
$\begin{array}{cl}
= & 1 – \dfrac{1}{28} \\
= & \dfrac{27}{28}
\end{array}$
