A hydraulic jack of the type shown in Fig. 22.10 is used to drive the piston of an extrusion press. The pressures on the two sides of the piston are 42 and 0-7 MN/m. The diameter of the piston is 150 mm and the diameter of the piston rod 50 mm. The lower pressure acts on the piston-rod side of the piston. Calculate the net force exerted by the jack. If the piston moves through a stroke of 0-6 m in 20s, find the average power developed. Fig. 22.10