Algorithm preorderDraw draws a binary tree T by assigning x- and y-coordinates to each position p such that x(p) is the number of nodes preceding p in the preorder traversal of T and y(p) is the depth of p in T.

a. Show that the drawing of T produced by preorderDraw has no pairs of crossing edges.

b. Redraw the binary tree of Figure 8.19 using preorderDraw.

2 3 5 7 8 9 10 12 0- 2---- 3- 4--