A steel shaft is to be force-fitted into a fixed-ended cast-iron hub. The shaft is subjected to a bending moment M, a torque T, and a vertical force P as shown. Suppose that at a point Q in the hub, the stress field is represented by σx=?, σy=4.6, σz=-8.3, τxy=-4.7, τxz=6.45, τyz=11.8 (MPa). If we decide to limit the maximum shear stress in the element to 25 MPa, determine the allowed range of σx. Note: The maximum shear stress or maximum principal shear stress is equal to one-half the difference between the largest and smallest principal stresses. Hint: Write a user-defined function which takes σx as input, sets up the stress matrix, calculates the maximum shear stress (Tmax), and returns y = Tmax - 25 as output. Then find the value of σx such that y = 0. Answer: -35.645 ≤ σx ≤ 32.083 MPa.