Consider the following four sets of values: [25, 18, 12, 10, 6, 7] [10, 8, 7, 6, 5, 4] [20, 15, 18, 12, 13, 11] [5, 7, 10, 12, 15, 18] For each set, determine whether it is a max-heap, a min-heap, or neither a max-heap nor a min-heap, and explain your reasoning.