1. **State the problem:** We need to find the mass of a metal prism with a given cross-sectional shape and length. The density of the metal is 8 grams per cm³. 2. **Understand the shape and dimensions:** The cross-section is an L-shaped polygon with outer vertical length 7 cm, outer horizontal length 7 cm, inner vertical segment 2 cm, and inner horizontal segment 2 cm. 3. **Calculate the area of the cross-section:** - Calculate the area of the large rectangle: $7 \text{ cm} \times 7 \text{ cm} = 49 \text{ cm}^2$ - Calculate the area of the small cut-out rectangle: $2 \text{ cm} \times 2 \text{ cm} = 4 \text{ cm}^2$ - Area of L-shape = $49 - 4 = 45 \text{ cm}^2$ 4. **Calculate the volume of the prism:** - Length of prism = 2 m = 200 cm - Volume = cross-sectional area $\times$ length = $45 \text{ cm}^2 \times 200 \text{ cm} = 9000 \text{ cm}^3$ 5. **Calculate the mass:** - Density = 8 grams/cm³ - Mass = density $\times$ volume = $8 \times 9000 = 72000$ grams 6. **Convert mass to kilograms if needed:** - $72000$ grams = $72$ kilograms **Final answer:** The mass of the prism is $72000$ grams or $72$ kilograms.