Find the hydrostatic force and centre of pressure on a 4 ft × 3 ft plate inclined at 30°, upper edge 64 ft below the free surface (γ = 62.4 lbf/ft^{3}). [The 4 ft side runs along the slope.] Give (a) the force in lbf and (b) the vertical distance of the centre of pressure below the centroid in ft.