An aircraft fuselage is 180" in diameter to the midplane of the skin, which is 0.063" thick 7075-T6 Al Sheet (Ftu=79 ksi, E=10.5 Msi). If the aircraft is pressurized each flight to a maximum differential pressure of 9.1 psi, and a factor of safety of 2.0 is required for evaluating static strength against ultimate pressure, assume the skins carry the pressure load alone (frame assistance is negligible) & determine the maximum ultimate principal stresses in the skin, and the minimum ultimate (static) margin of safety.