Write a method called printLevel that accepts an integer parameter n and prints the values at level n from left to right, one per line. We will use the convention that the overall root is at level 1, its children are at level 2, and so on. If there are no values at the level, your method should produce no output. Your method should throw an IllegalArgumentException if it is passed a value for a level that is less than 1. For example, if a variable t refers to reference tree #2, then the call of t.printLevel(3); would produce the following output:

0

7

6

Reference Tree #2 2 Reference Tree #1 1 7. 4 4 Reference Tree #3 2 3 8. 9. 3. 1.