A multiple-disc clutch transmits 50 kW of power at 1400 r.p.m. Axial intensity of pressure is not to exceed 0.15 N/mm, and the coefficient of friction for the friction surfaces is 0.12. The inner radius of the disc is 80 mm which is 0.7 times the outer radius. Determine the number of discs required to transmit the given power. Assume uniform wear condition. (a) 12 (b) 8 (c) 4 (d) 14