Draw the recursion trace for the execution of function Prints {3, S, U), where S is empty and U = {a, b, c, d}. List all the printouts of S. Algorithm Prints (k, S, U) :Input: An integer k, sequence S, and set U Output: An enumeration of all k-length extensions to 5 using elements in U without repetitions for each e in U do Remove e from U [e is now being used} if k - 1 then Print S else Prints, U) Add e back to V (e is now unused) Remove e from the end of S