${\left({\mathrm{CH}}_3\right)}_3\mathrm{C}-\mathrm{Br} \stackrel{\mathrm{Zn}/{\mathrm{H}}^{+}}{\to } \mathrm{A} \stackrel{{\mathrm{KMnO}}_4}{\to } \mathrm{B}.$ The product be in this process is

In the first step, alkyl undergoes dehalogenation in the presence of zinc/acid where halogen is replaced by a hydrogen. In the next step, oxidation occurs in the presence of KMnO₄.

${\left({\mathrm{CH}}_3\right)}_3\mathrm{C}-\mathrm{Br} \stackrel{\mathrm{Zn}/{\mathrm{H}}^{+}}{\to } \underset{\mathrm{A}}{{\left({\mathrm{CH}}_3\right)}_3\mathrm{CH}} \stackrel{{\mathrm{KMnO}}_4}{\to }\underset{\mathrm{B}}{ {\left({\mathrm{CH}}_3\right)}_3\mathrm{C}-\mathrm{OH}}$