A satellite describes a circular orbit at an altitude of 19110 km above the surface of the earth. Determine (a) the increase in speed required at point $A$ for the satellite to achieve the escape velocity and enter a parabolic orbit, (b) the decrease in speed required at point $A$ for the satellite to enter an elliptic orbit with a minimum altitude of 6370 km , (c) the eccentricity $\varepsilon$ of the elliptic orbit.