figure: ar-a3-window.png A window is a rectangle 84 cm wide and 100 cm high, with a semicircle on…

Step 1. The rectangle. $84 \times 100 = 8400\ \text{cm}^2$.

Step 2. The semicircle. $\dfrac{1}{2} \times \dfrac{22}{7} \times 42 \times 42 = 2772\ \text{cm}^2$.

Step 3. The glass. $8400 + 2772 = 11\,172\ \text{cm}^2$.

Step 4. The frame. The curved top is $\dfrac{22}{7} \times 42 = 132\ \text{cm}$. The frame is $84 + 100 + 100 + 132 = 416\ \text{cm}$.