Charles and Bernice ("Ray") Eames were American designers who made major contributions to modern architecture and furniture design. Suppose that a manufacturer wants to make an Eames elliptical coffee table 78 in long and 62 in wide out of an 8 ft by 4 ft piece of birch plywood. If the center of a piece of plywood is positioned at (0, 0), determine the distance from the center at which the foci should be located to draw the ellipse. Express numbers in exact, simplest form.