Given the valid binary search tree $($BST$)$ below, if you are performing a search and your target key is $18,$ how many nodes will you visit before you find it$?($taking advantage of the properties of a BST$)$

Now assume you don't know if you have a valid BST$,$ and you are performing a Breadth First Search on the tree to find $18.$ How many nodes will you visit before you find it$?$

Explain how you determined both numbers.