The two reactants shown below are combined to bring about a nucleophilic substitution reaction.

e$.$

h$.HBr$

none

f$.B{r}^{-}$

i$.H_{2}O$

O

j$.N{a}^{+}$

g$.HOCC{H}_3$

Which letter designates the electrophilic carbon at which substitution occurs? $($If no reaction occurs enter the letter corresponding to "none."$)$

Which letter corresponds to the leaving group?

Which letter designates the nucleophile?