Your question is Wing Spar Maximum Bending Stress. Take a moment with it on the right.
Talk me through your thinking if you like. When you're confident, submit your answer and I'll grade it like a real screen (7/10 or better passes).
Given the spanwise bending moment distribution for an aluminum alloy I-beam wing spar under aerodynamic lift, how would you determine the maximum bending stress in the spar? Also, explain how material fatigue considerations affect the design.