A certain voltage is $+13\mathrm{.}2$ V for $17\mathrm{.}9$ ms and $-13\mathrm{.}2$ V for the succeeding $17\mathrm{.}9$ ms and continues oscillating back and forth between these two values at $35\mathrm{.}8$ ms intervals.

The voltage is present across a $59$ resistor.

Over any $35\mathrm{.}8$ ms interval, find:

$($a$)$ the maximum value of the voltage

$($b$)$ the average value of the voltage

$($c$)$ the average value of the resistor current