This question is a minor adaptation of Example 3 from Week 7, L1 (slide

32), using the same cross-section and extreme-fibre distances but a different

bending moment. An unsymmetric beam cross-section has a second moment of area I

= 419 × 10⁴ mm⁴ about the neutral axis. The extreme fibres are located at y =

41.25 mm (top) and y = –93.75 mm (bottom). If the section carries a bending

moment of –4000 N·m (note: the original lecture example used –3600 N·m), what

is the bending stress at the bottom fibre (y = –93.75 mm)?