Answer
The rectangular coordinates are $(0,-4)$
Work Step by Step
We can find the x-coordinate:
$x = r~cos~\theta$
$x = (-4)~cos~90^{\circ}$
$x = (-4)~(0)$
$x = 0$
We can find the y-coordinate:
$y = r~sin~\theta$
$y = (-4)~sin~90^{\circ}$
$y = (-4)~(1)$
$y = -4$
The rectangular coordinates are $(0,-4)$
