1. **State the problem:** We have a prism with a regular decagon as its cross-section. Each side of the decagon is 2 cm, and the height of the prism is 12 cm. We want to find: a) The area of each rectangular face of the prism. b) The total area of all the rectangular faces. 2. **Formula and explanation:** Each rectangular face corresponds to one side of the decagon and the height of the prism. The area of one rectangular face is given by: $$\text{Area} = \text{side length} \times \text{height}$$ Since the prism has 10 sides (decagon), the total area of the rectangular faces is: $$\text{Total area} = 10 \times \text{area of one rectangular face}$$ 3. **Calculate the area of one rectangular face:** $$\text{Area} = 2 \text{ cm} \times 12 \text{ cm} = 24 \text{ cm}^2$$ 4. **Calculate the total area of the rectangular faces:** $$\text{Total area} = 10 \times 24 \text{ cm}^2 = 240 \text{ cm}^2$$ **Final answers:** a) The area of each rectangular face is $24 \text{ cm}^2$. b) The total area of the rectangular faces is $240 \text{ cm}^2$.