7. (10%) f(n) = (g(n)) if and only if there exist positive constants C1, C2, and no such that cg(n) = f(n) = c2g(n) for all n > no. Prove or disprove the following statements are correct. (To get the score, you need to prove your answer. No score if you only answer true or false). (a) (5%) 5n? 6n = @(n). (b) (5%) nlogn = (n)