b
(b) \(C{H_3} - \mathop {\mathop {C\, - \,}\limits_{|\,\,\,\,\,\,}^{|\,\,\,\,\,\,\,} }\limits_{C{H_3}}^{C{H_3}} Br + C{H_3}ONa\xrightarrow{{{\text{Elimination}}}}\) 

 \(\mathop {C{H_3} - \mathop {\mathop {C\,\, = \,}\limits^{|\,\,\,\,\,\,} }\limits^{C{H_3}} C{H_2}}\limits_{{\text{Isobutylene}}}  + C{H_3}OH + NaBr\)

\(C{H_3}ONa \to C{H_3}{O^ - } + N{a^ + }\)

methoxide ion  is a \((C{H_3}{O^ - })\)strong base, therefore it abstract proton from \(3^\circ\)alkyl halide and favours elimination reaction.