I am COMPLETELY stumped with this question. Can someone help me get started on a couple of steps? Hints? Thank you so much.

Streelights A, B, C, D, and E are placed 50 m apart on the main road. The light from a streetlight is effective up to a distance of 60m.

a. Determine the distance from A to the farthest point on the side road that is effectively illuminated.

b. Determine the length of the side road that is effectively illuminated by both streetlights C and D.

http://img245.imageshack.us/img245/9306/imagedja.jpg

Thank you!