Solution

The bottom left corner of the rectangle is at the center of curvature of the mirror, so its image remains at that point. The top left corner of the rectangle and its image are symmetric with respect to the principal axis. The bottom right corner of the rectangle is at the focal point of the mirror, so its image is on the principal axis at infinity. The image of the top right corner of the rectangle is also at infinity. Since the top side is parallel to the principal axis, its image is on a line through the focal point. In the figure, the rectangle is shown with thin lines, while its image is shown with thick lines.