Write a method called countEmpty that returns the number of empty branches in a tree. An empty tree is considered to have one empty branch (the tree itself). For nonempty trees, your methods should count the total number of empty branches among the nodes of the tree. A leaf node has two empty branches, a node with one nonempty child has one empty branch, and a node with two nonempty children has no empty branches. For example, reference tree #1 has 7 empty branches (two under the value 1, one under 5, and two under each of 4 and 6).

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