Ans: (a) $\dfrac{10}{21}$ (b) $\dfrac{11}{21}$
- The required probability
$\begin{array}{cl}
= & \dfrac{C^5_2\times C^4_2}{C^9_4} \\
= & \dfrac{10}{21}
\end{array}$ - The required probability
$\begin{array}{cl}
= & 1-\dfrac{10}{21} \\
= & \dfrac{11}{21}
\end{array}$
