Halley's Comet, which passes around the Sun every 76 years, has an elliptical orbit. When closest to the Sun (perihelion) it is at a distance of 8.823 × 1010 m and moves with a speed of 54.6 km/s. The greatest distance between Halley's Comet and the Sun (aphelion) is 6.152 × 1012 m.

(a) Is the speed of Halley's Comet greater than or less than 54.6 km/s when it is at aphelion? Explain.

(b) Calculate its speed at aphelion.