Do a careful hand simulation of computation of sum(4) using the following definition of sum. Show how variables k and r change, and what the answer is.
  Define
    sum(n) = r |
      Let k = 1.
      Let r = 0.
      While k <= n do
        Relet r = r + k.
        Relet k = k + 1.
      %While
  %Define