Which sequence correctly lists the methyl halides in increasing order of rate of SN2 reaction with a given nucleophile?

In SN2 the halide leaves in the rate-determining step, so a better leaving group means a faster reaction. Leaving ability follows the weakness of the C-X bond and the stability of $\mathrm{X}{}^{-}$: $\mathrm{I}{}^{-}>\mathrm{Br}{}^{-}>\mathrm{Cl}{}^{-}>\mathrm{F}{}^{-}$. Hence the rate increases from $\mathrm{CH}{}_3\mathrm{F}$ to $\mathrm{CH}{}_3\mathrm{I}$.