It takes 27 days for the Moon to orbit the Earth in a nearly circular orbit of

Question:

It takes 27 days for the Moon to orbit the Earth in a nearly circular orbit of radius 3.80 x 105 km.
(a) Show in symbol notation that the mass of the Earth can be found using these data.
(b) Compute the Earth’s mass and com-pare with the value given inside the back cover of the book.