b) The vertical height (in feet) of an elevator as a function of time (in seconds) is represented by the equation

h = -5t + 145

How fast does the vertical height change, in feet per second?

c) What direction is the elevator moving in part b?

d) The vertical position, h, in meters, of a fly ball as a function of time, t, in seconds, is approximated by the equation

h = -5t^{2} + 20t + 2

After how many seconds will the ball not be moving for an instant?