A cross section of an airplane fuselage made of aluminum alloy is shown in Figure P6.112. For an applied torque of T = 1,250 kip-in. and an allowable shear stress of τ = 7.5 ksi, determine the minimum thickness of the sheet (which must be constant for the entire periphery) required to resist the torque. (Note: The dimensions shown are measured to the wall centerline.)