16. Define recursion in programming languages (PL). Must a PL support recursive functions and calls? Can an inherently recursive problem be solved in a PL that does not support recursive calls? If not, why not? If so, how? 17. What does the below logic statement mean in plain English? Demonstrate your answer via an example: Vab (a - b = 100) 20. Prove informally, pro or con, which set is larger: The set N of all integer numbers, or the set R of all real numbers?