A centrifugal clutch is to transmit 15 kW at 900 rpm The shoes are four in number. The speed at which the engagement begins is 3/4th of the running speed. The inside radius of the pulley rim is 150 mm and the centre of gravity of the shoe lies at 120 mm from the centre of the spider. The shoes are lined with Ferrodo for which the coefficient of friction may be taken as 0.25. Determine the mass of the shoes, if the angle subtended by the shoes at the centre of the spider is 60 and the pressure exerted on the shoes is 0.1 MPa.