申論題

7.[15] Suppose we have 12 integers: 60, 40, 25, 10, 50, 80, 15, 65, 30, 90, 20, 55. Construct a binary search tree by inserting the integers, starting from 60, one after another. Please answer the following questions for the binary search tree:

7.1 [3] What is the left child of the root node?