4.如圖示之樑，若最大正彎矩與最大負彎矩之大小相等，試問外力P為何？

2. A pressurized cylindrical tank with flat ends is loaded by torques T and tensile forces P as shown in Fig. 2. The tank has inner radius of r = 125 mm and wall thickness t = 6.5 mm. The internal pressure p = 7.25 MPa and the torque T = 850 N-m. What is the maximum permissible value of the forces P if the allowable tensile stress in the wall of the cylinder is 80 MPa? (20%)Fig. 2