The steel tube has an elliptical cross section of mean dimensions shown and a constant thi...

The steel tube has an elliptical cross section of mean dimensions shown and a constant thickness of t = 0.2 in. If the allowable shear stress is τallow. =8 ksi. and the tube is to resist a torque of T = 250 lb • ft, determine the necessary dimension b.The mean area for the ellipse is Am = πb(0.5b).