Show how to use property 2 of Lemma 16.12 to determine in time O(|A|) whether or not a given set A of tasks is independent.

Lemma 16.12
For any set of tasks A, the following statements are equivalent.
1. The set A is independent.
2. For t = 0, 1, 2, . . . , n, we have N_t(A) ≤ t.
3. If the tasks in A are scheduled in order of monotonically increasing deadlines, then no task is late.