4. A full binary tree is a tree whose leaves are all at the same level, and every node that is not a leaf has exactly two nodes under it. FIGURE 1.36 is a full binary tree with three levels. *

(a) Draw the full binary tree with four levels. *

(b) How many nodes total are in a full binary tree with five levels?

(c) With six levels?

(d) With n levels in general?