An asteroid experiences an attractive force of 1.0×103N from Earth when its centre is 4.0×107m from Earth’s centre. If Earth’s mass is 6.0×1024kg and G=6.67×10−11N m2kg−2, the mass of the asteroid is closest to
a) 4.0×102kg
b) 4.0×106kg
c) 4.0×103kg
d) 1.0×103kg