I have no idea how to start this, let alone finish it. The worst part is I have to solve it by the end of tonight! Would one of you guys please help me?

Oh yeah: can I assume triangle BST is an equilateral triangle?

Solve using a two column proof:

Given: Line segment AS is parallel to line segment BT;

The measure of angle 4 is equal to the measure of angle 5

Prove: Ray SA bisects angle BSR

Thank you!