An 80 kg man stands in an elevator. What force does the floor of the elevator exert on the man if

a) the elevator is stationary?
b) the elevator accelerates upward at 2 m/s2?
c) the elevator rises with constant velocity 4 m/s?
d) while rising, the elevator decelerates at 1.5 m/s2?
e) the elevator descends with constant velocity 7 m/s?

Please show step by step with the equations for each one