Prime numbers = Those numbers which are divisible by 1 and number itself.
Prime numbers = 2, 3, 5, 7, 11, 13,…, 83, 89, 97, …
Prime number greater than 90 = 97
Prime number less than 96 = 89
Prime number less than 96 but greater than 90 = ɸ
∴ The set is empty
∴ It is a null set