A 500kg satellite is to be shifted from a circular orbit of radius 2R⊕ to a circular orbit of radius 4R⊕ around the Earth. Ignore atmospheric drag. How much work must be done on the satellite (positive if energy must be supplied)?
(a) −3.9×109J
(b) 1.95×109J
(c) 3.9×109J
(d) 7.8×109J