Note: In the following, A*B*C means B is between A and C.

1. Recall that Problem 5 of Section 1.2 says: If B*A*C and B*P*A, then B*P*C. Now, assume we are given four distinct collinear points, X, Y, Z, and W, such that X*Y*Z and X*Z*W. Which of the following follows directly from Problem 5: X*Y*W, or Y*Z*W, or both? Prove your answer.
2. (Optional -- Extra Credit) Assume we are given four distinct collinear points, X, Y, Z, and W, such that X*Y*Z and Y*Z*W. Prove that X*Y*W.