7. Establish the following divisibility criteria: (a) An integer is divisible by 2 if and only if its units digit is 0, 2, 4, 6, or 8. (b) An integer is divisible by 3 if and only if the sum of its digits is divisible by 3. (c) An integer is divisible by 4 if and only if the number formed by its tens and units digits is divisible by 4. [Hint 10" E 0 (mod 4) for k 2 2.] In. a a. a a A u