The cross section of the aluminum tube shown transmits a torsional moment of 500 lb-in. Let E=10 Mpsi and ν =0.33. The section, dimensioned in inches, is symmetric with respect to the y and z-axes. The 1.0-in dimensions are between wall centerlines, and the centerlines of the 0.25-in vertical walls align with the centerlines of the ends of the circular walls. Determine the average shear stress in each wall and angle of twist over a length of 24 in.