5. (a) Write a recursive function that calculates n factorial, i.e., n! (b) Write a recurrence relation for the time complexity of the function in part (a). Justify your answer. Express this time complexity using in Big-O notation. Justify your answer again. (c) Does the time complexity of the function changes once you have the iterative version (non-recursive) of the factorial function? Write the corresponding algorithm and analyze it in the worst-case time complexity