$(a)$ $CH_3CH_2CH_2CH_2Br$
$(b)$ $\begin{matrix}
\begin{matrix}
\,\,\,\,\,\,C{{H}_{3}} \\
| \\
\end{matrix} \\
{{H}_{3}}C-C-C{{H}_{3}} \\
| \\
\,\,Br \\
\end{matrix}$
$(c)$
$I.$ $C H_{3} C H=C H C H_{3}$ (મુખ્ય નીપજ )
$II.$ $C H_{2}=C H C H_{2} C H_{3}$ (ગૌણ નીપજ )