Let be a rooted tree with 13 nodes, in which each node has either two or zero children. The leaves of this tree are 1,2,3,4,5,6,7, and the non-leaves are ,,,,,; the names of these leaves and non-leaves are not in any particular order. We run the algorithm (), where is the root of . This algorithm generates recursive calls to (), in the following order ,,,2,7,,1,5,,4,,6,3. What is the number of nodes in the subtree rooted at node ? (Note that the node is included in the count.) Select one: a. 3 b. 5 c. 7 d. 1