$22.$ A manufacturing facility uses methyl mercaptan to produce a jet fuel additive. The rupture disk on a tank containing $2,500$ lbs of methyl mercaptan fails, releasing the entire contents to the atmosphere as a vapor. The tank is in the middle of a congested tank farm, and the release is on a calm day $($wind speed $<1\mathrm{.}5$ m$/$s$).$ Based on the Guidance for Off$-$site Consequence Analysis, what is worst case toxic endpoint of the methyl mercaptan cloud.

a$.7\mathrm{.}0$ miles

b$.2\mathrm{.}0$ miles

c$.0\mathrm{.}7$ miles

d$.0\mathrm{.}2$ miles