Consider the following data: the period of the Moon's revolution around Earth is 28 days, the average radius of Earth is 6400 km, and the free-fall acceleration of objects near Earth's surface is g = 9.8 m/s^2. A camera takes two pictures two minutes apart which shows the moon had moved its entire diameter in that time (relative to the viewer). If the average distance between the Earth and the Moon is 3.9 x 10^8 m, estimate the diameter of the Moon.