b
\(\begin{array}{*{20}{c}}
  {O\,\,\,\,\,} \\ 
  {||\,\,\,\,\,} \\ 
  {C{H_3} - C - O{C_2}{H_5}} 
\end{array}\, + \,C{H_3}MgI\, \to \,\begin{array}{*{20}{c}}
  {\,\,\,OMgI} \\ 
  {|\,\,\,\,\,\,} \\ 
  {C{H_3} - C - O{C_2}{H_5}} \\ 
  {|\,\,\,\,\,\,\,} \\ 
  {C{H_3}} 
\end{array}\)

\(\xrightarrow{{{H_2}O/{H^ + }}}\begin{array}{*{20}{c}}
  O \\ 
  {||} \\ 
  {C{H_3} - C - C{H_3}} 
\end{array}\, + \, Mg < \begin{array}{*{20}{c}}
  {O{C_2}{H_5}} \\ 
  I 
\end{array}\)

\(\xrightarrow[{(ii)\,{H_2}O/{H^ + }}]{{(i)\,C{H_3}MgI}}\begin{array}{*{20}{c}}
  {OH} \\ 
  | \\ 
  {C{H_3} - C - C{H_3}} \\ 
  | \\ 
  {\,\,\,\,\,C{H_3}} 
\end{array}\, + \, Mg < \begin{array}{*{20}{c}}
  {OH} \\ 
  I 
\end{array}\)

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