The geocentric equatorial position vectors, in km, of a satellite at three separate sightings are: r1 = 2800 i + 6000 j + 9000 k r2 = ‒ 3500 i + 227 j + 12400 k r3 = ‒ 13000 i ‒ 7000 j + 9200 k using gibbs method, a) determine the orbit eccentricity b) is the orbit retrograde or prograde? c) what is the perigee altitude of the satellite?