At a given section a shaft is subjected to a bending stress

Question

At a given section a shaft is subjected to a bending stress of 20 MN/m² and a shear stress of 40 MN/m². Determine:

(a) the principal stresses;

(b) the directions of the principal planes;

(c) the maximum shear stress and the planes on which this acts;

(d) the tensile stress which, acting alone, would produce the same maximum shear stress;

(e) the shear stress which, acting alone, would produce the same maximum tensile principal stress.