In the following tree, how many leaf nodes are there?

A tree structure. The tree structure shows a root node labeled age $=30.$ The root node splits into node $1$ and node $2.$ Node $1$ is labeled income $$85,000.$ Node $2$ is labeled income $$45,000.$ Node $1$ splits into node $3$ and node $4.$ Node $2$ splits into node $5$ and node $6.$ Node $3$ is labeled approved. Node $4$ is labeled declined. Node $5$ is labeled approved. Node $6$ is labeled declined.

Multiple Choice

four

two

six

seven