$ 3 \mathrm{ROH}+\mathrm{PCl}_3 \rightarrow 3 \mathrm{RCl}+\mathrm{A} $
$ \mathrm{ROH}+\mathrm{PCl}_5 \rightarrow \mathrm{RCl}+\mathrm{HCl}+\mathrm{B}$
\(3 \mathrm{ROH}+\mathrm{PCl}_3 \longrightarrow 3 \mathrm{RCl}+\mathrm{H}_3 \mathrm{PO}_3\)(A)
\(\mathrm{ROH}+\mathrm{PCl}_5 \longrightarrow \mathrm{RCl}+\mathrm{HCl}+\mathrm{POCl}_3\)(B)
\(A\) and \(B\) are \(\mathrm{H}_3 \mathrm{PO}_3\) and \(\mathrm{POCl}_3\) respectively.
$(a)$ $CH_3CH_2CH_2CH_2Br$
$(b)$ $\begin{matrix}
\begin{matrix}
\,\,\,\,\,\,C{{H}_{3}} \\
| \\
\end{matrix} \\
{{H}_{3}}C-C-C{{H}_{3}} \\
| \\
\,\,Br \\
\end{matrix}$
$(c)$
$C{H_3}C{H_2}C \equiv CH\, + \,HCl\, \to \,B\,\xrightarrow{{HI}}C$