A simple pendulum is $8\mathrm{.}20$ m long.

$($a$)$ What is the period of simple harmonic motion for this pendulum if it is located in an elevator accelerating upward at $5\mathrm{.}75$ m$/$s$2?$

$4\mathrm{.}56$ s

$($b$)$ What is its period if the elevator is accelerating downward at $5\mathrm{.}75$ m$/$s$2?$

$8\mathrm{.}94$ s

$($c$)$ What is the period of simple harmonic motion for the pendulum if it is placed in a truck that is accelerating horizontally at $5\mathrm{.}75$ m$/$s$2?$