4. What value is returned by the following function? Express your answer as a function of . Give the worst-case running time complexity. All logic/mathematical derivations must be clear. function mystery(n) i. r-0 ii. for i-1 to (n-1) iii for j (i+1) to n do iv, for k = 1 to j do V. r=r+1 vi. return (r)