(20 pts) The cross-section of a thin-walled, prismatic beam is shown below. The thickness t is uniform everywhere, and a and a are known constants. The beam is cantilevered and is subjected to a vertical tip load P through point B. (a) Find the torsion constant J. (b) Find the location of the shear center. (c) Find the maximum shear stress and its location in the cross-section. a a a ZA a a ------------- B X