1. create a method for Binary Search Tree class that prints the values of the tree in post order traversal form. Write both the needed public and a private methods.
2. Suppose that s and t are empty stacks and a, b, c, d are objects. What do the stacks contain after the following sequence of operations executes?

s.push(a);

s.push(b);

s.push(c);

t.push(s.peek());

t.push(s.pop());

t.push(s.peek());