Identify the halogen exchange reaction from the following.

Finkelstein reaction: It is an ${\mathrm{S}}_{\mathrm{N}}2$ reaction (substitution nucleophilic bimolecular reaction) that involves an exchange of one halogen atom for another. It is an organic reaction, which uses an alkyl halide exchange into another alkyl halide through a reaction, wherein the metal halide is used.

Reaction with halides:

$\underset{\mathrm{Alkyl} \mathrm{halide}}{\mathrm{RCl}}+ \mathrm{NaBr}\to \underset{\mathrm{Alkyl} \mathrm{bromide}}{\mathrm{RBr}}\stackrel{\mathrm{NaI}}{\to } \underset{\mathrm{Alkyl} \mathrm{iodide}}{\mathrm{RI}}$