Steve has a mass of 85 kg and wears size 11 shoes. The bottom of each of Steve's shoes has an area of 0.03 m2 (approximately 30 cm by 10 cm). What pressure do the soles of Steve's shoes exert on the ground when

(a) he is standing still?
(b) he is standing on one leg?
(c) he is in the process of jumping (with both feet on the ground), and thus accelerating upwards at a rate of 5 ms−2.