Whenever two Apollo astronauts were on the surface of the Moon, a third astronaut orbited the Moon. Assume the orbit to be circular and $100 \mathrm{~km}$ above the surface of the Moon. If the mass of the Moon is $7.40 \times 10^{22} \mathrm{~kg}$ and its radius is $1.70 \times 10^{6} \mathrm{~m}$, determine (a) the orbiting astronaut's acceleration, (b) his orbital speed, and (c) the period of the orbit.