chain rule - calculus problem

Question

A crate of supplies is dropped from an airplane at an altitude of 3000 meters. Its height, as a function of time, is

h(t) = 3300 − 54t − 300e^−0.18t

where h is in meters and t is in seconds. Answer the following questions. All answers must have correct units.

1. The crate has a parachute system that is set to open when the crate reaches the height of 2000 meters. At that instant, how fast is it moving? Be accurate to one decimal place. _______

Answer 1

H’(t)=54+300*0.18e^-0.18t

2000=3300-54t-300e^-0.18t

^t=23.5

^{h’(23.5)=54.8}