When the Earth, Moon, and Sun form a right triangle with the Moon located at the right angle, as shown in the figure below, the Moon is approaching its third quarter. (The Earth is viewed here from above its north pole.) Find the magnitude and direction of the net force exerted on the Moon. Give the direction relative to the line connecting the Moon and the Sun.
Figure: http://www.webassign.net/walker/12-21alt.gif

answers in N for first question and ° counterclockwise from the Moon-to-Sun ray for second question.

I have no idea how to do this question. Thank you!

Question

When the Earth, Moon, and Sun form a right triangle with the Moon located at the right angle, as shown in the figure below, the Moon is approaching its third quarter. (The Earth is viewed here from above its north pole.) Find the magnitude and direction of the net force exerted on the Moon. Give the direction relative to the line connecting the Moon and the Sun. 
Figure: http://www.webassign.net/walker/12-21alt.gif

answers in N for first question and ° counterclockwise from the Moon-to-Sun ray for second question.

I have no idea how to do this question. Thank you!