the moon has a mass of 1×1022 kg, and the gravitational field strength at a distance r from the planet is 0.001 n/kg. what is the gravitational force exerted on the moon while it is in orbit around the planet?
a. 0 N
b. 1 x 10^19 N
c. 1 x 10^22 N
d. 1 x 10^25 N