1. **Stating the problem:** Calculate the moment resistance $M_p$ of a rectangular cross-section given the area $A = 8000$ cm$^2$, allowable stress $S_e = 250$ MPa, and dimensions height $h = 150$ mm, base segments $10$, $80$, and $10$ mm. 2. **Formula used:** The plastic moment resistance $M_p$ is calculated by $$M_p = S_e \times Z_p$$ where $Z_p$ is the plastic section modulus. 3. **Calculate the plastic neutral axis (PNA):** Since the section is symmetric about the vertical axis, the PNA is at mid-height, $h/2 = 75$ mm. 4. **Calculate the plastic section modulus $Z_p$:** The plastic section modulus for a rectangular section is $$Z_p = A \times \frac{h}{4}$$ where $A$ is the cross-sectional area and $h$ is the height. 5. **Convert units:** - Area $A = 8000$ cm$^2 = 8000 \times 100 = 800000$ mm$^2$ - Height $h = 150$ mm 6. **Calculate $Z_p$:** $$Z_p = 800000 \times \frac{150}{4} = 800000 \times 37.5 = 30000000 \text{ mm}^3$$ 7. **Calculate $M_p$:** $$M_p = 250 \times 30000000 = 7.5 \times 10^9 \text{ Nmm}$$ 8. **Convert $M_p$ to kNm:** $$M_p = \frac{7.5 \times 10^9}{10^6} = 7500 \text{ kNm}$$ **Final answer:** $$M_p = 7500 \text{ kNm}$$