3. Determine the output value that is returned by the following algorithm. Express your solution as a function of n. Provide the complexity of the worst case of the algorithm in terms of n, and then using the notation O(n). Determine the operations used. function expression (n) r:=0 for i:=1 to n-1 do for j:=i+1 to n do for k:= 1 to j do r := r + 1 return (r)