Complete each of the following statements below using the figure below.
\[
\mathrm{H}_{3} \mathrm{C}-\mathrm{Br}+\mathrm{NaOCH}_{3} \longrightarrow
\]
a. In the above reaction, \( \square \) [Select] is the nucleophile.
b. In the above reaction, \( \square \) [Select] is the electrophile.
c. In the above reaction, \( \square \) [Select] is the leaving group.
c. The above reaction should proceed via an \( \square \) [Select] mechanism.