For a certain hypothetical planet revolving around a star the total mechanical energy is given as $E=-\frac{GMm}{40l}$ , where M is the mass of the star, m is the mass of the planet, $l$   is a certain distance and it is given that  $M>>m$ . The distance between the planet and the centre of the star at the perihilion position is 4l. The velocity of the planet at perihilion is  $V_p$  and that at the aphelion  $V_{\alpha }$   and the ratio $\frac{V_p}{V_{\alpha }}=\eta$ . Then what must be the value of  $\eta$.