The stresses acting on the plane of maximum shearing stress by a given point in sand are as follows: total normal stress = 250 kN/m²; pore-water pressure = 88.5 kN/ m²; shearing stress = 85 kN/m². Failure is occurring in the region surrounding the point. Verify the major and minor principal effective stresses, the normal effective stress and the shearing stress on the plane of failure and the friction angle of the sand. Explain clearly the terms 'plane of maximum shearing stress' and 'plane of failure' in relation to the Mohr's rupture diagram.