Answer
When $t=2$, $528.1$ feet.
When $t=4$, $336.1$ feet.
Work Step by Step
$-16t^2 + 592.1$
$=-16(2)^2 + 592.1$
$=-16(4)+592.1$
$=-64+592.1$
$=528.1$ feet
$-16t^2 + 592.1$
$=-16(4)^2 + 592.1$
$=-16(16)+592.1$
$=-256+592.1$
$=336.1$ feet