Question

What is the height of the platform?

Answer 1

40 metres.. Hope this helps u

Answer 2

It's 40 ft.

Since the rocket is launched from a platform, then the height of the rocket at 0 seconds will be the height of the platform.
$h(t)=-16t^{2}+70t+40\\h(t)=-16(0)^{2}+70(0)+40\\h(t)=0+0+40=40ft$