(a) $CH_{3}Br\ + \ OH^{-}\ \rightarrow \ CH_{3}OH\ + \ Br^{-}\$ This reaction proceeds by $S_{N}2$ mechanism. Rate $\propto$ [substrate][nucleophile] Rate $\propto \ \lbrack CH_{3}Br\rbrack\lbrack OH^{-}\rbrack$
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.