Please help me solve this statistic question

The actuating force (F) necessary to apply the brake shown in the gure below is given by 1 F = 5'1\"\" Mr], where 92 1 . Mn = pa .1 r b (3 Esmsz) M; = p,1 t rf (r rcosz 55111292) with the foiiowing pljl =maximum pressure exerted on the brake lining (Pa), t =face width of the brake shoes (m), r =inner radius of the brake drum (m), b =radius of the brake shoe (m), f =coefcient of friction, a =iinear distance between the brake shoe hinge and the line of application of the actuating force (m), and 62 =angle between the brake shoe hinge and the point of application of the actuating force. Rotation Brake lining of rim \f