Velocity of stone after 4 sec

Question

If a stone is thrown vertically upward from the surface of the moon with a velocity of 14 m/s, its height (in meters) after t seconds is h = 14t - 0.83t2. (Round the answers to two decimal places.)
What is the velocity of the stone after 4 s?

Answer 1

h(t) = -0.83t² + 14t

 

v(t) = dh/dt = -1.66t + 14

 

v(4) = [-1.66(4) + 14] sec = ? sec