Let vp be the speed of a planet at perihelion in an elliptical orbit of semi-major axis a and eccentricity e. Let vc be the speed of a satellite moving in a circular orbit of radius a around the Sun. Which expression gives the ratio vp/vc in terms of e?
a) 1−e1+e
b) 1+e1−e
c) 1−e1+e
d) 1−e21+e2