A 1000kg satellite revolves round the Earth in a circular orbit of radius 3R⊕, where R⊕=6.4×106m. Take G=6.67×10−11N m2kg−2 and M⊕=6.0×1024kg. The binding energy (magnitude of total mechanical energy) of the satellite is closest to
a) 5.2×109J
b) 2.0×1010J
c) 1.0×1010J
d) 7.8×109J