18. (Total Score: 12 points) A unit uses wood to make a frame as shown in the figure. The lower part of the frame is a rectangle with sides $x$ and $y$ (in meters). The upper part is an isosceles right triangle. The total area enclosed by the frame is required to be $8 \text{ m}^2$. Find the values of $x$ and $y$ (accurate to 0.001 m) that minimize the amount of material used. [Figure]
18. (Total Score: 12 points)\\
A unit uses wood to make a frame as shown in the figure. The lower part of the frame is a rectangle with sides $x$ and $y$ (in meters). The upper part is an isosceles right triangle. The total area enclosed by the frame is required to be $8 \text{ m}^2$. Find the values of $x$ and $y$ (accurate to 0.001 m) that minimize the amount of material used.\\
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