=== E1: one machine, minimize the sum of completion times ===
  job      :   j1   j2   j3   j4   j5   j6
  length   :    7    2    5    1    4    3
  SJF order:   j4   j2   j6   j5   j3   j1
    completion times:    1    3    6   10   15   22
    sum = 57,  average = 9.5000
  all 720 orders examined: best = 57, worst = 97
  SJF attains the best: YES
