A communication satellite must appear stationary with respect to an observer on Earth’s surface. The period of such a satellite is 24h. Using G=6.67×10−11N m2/kg2 and ME=5.97×1024kg, the required orbital radius (measured from Earth’s centre) is approximately
(a) 3.6×107m
(b) 4.2×107m
(c) 2.4×107m
(d) 8.6×107m