The red figure is the image of the blue figure after a dilation with center $C$ . Two rectangles and a point C are shown. A line is drawn from each vertex of the larger rectangle to point C, first passing through the corresponding vertex of the smaller rectangle. The length of the larger rectangle is labeled 28 and the width of the larger rectangle is labeled m. The length of the smaller rectangle is labeled 7 and the width of the smaller rectangle is labeled 4. Find the scale factor of the dilat