1            ___________
 2           /           \
 3          /   $2______$1    \
 4         /   $2/      \$1    \
 5         |  $2(        )$1    \
 6        /    $2\______/$1     |
 7        |                 |
 8       /                   \
 9       |                   |
10       |                   |
11      /                    |
12      |                    |
13      |     _______        |
14 ____/     /       \       |
15/          |       |       |
16|          /   ____/       |
17\_________/   /            |
18              \         __/
19               \_______/