A program consists of two parts that are executed sequentially. The size of the input is described by n. The first part has a time complexity that can be expressed as t(n) = 5n + 16 and the second part has the time complexity t(n) = 6n3+n + 18. Use only the definition of the big O notation, do not use any laws for the big O notation (unless you prove them as well). a) To which big O sets do t and t belong? b) To which big O set does the entire program belong? c) Prove that if f = O(91) and f2 O(92), then (fi + f2) O(max{91, 92}).