input: Write a python function to find the difference between the highest and lowest numbers in a list.
  assert diffHighestLowest([12, 24, 3, 8, -1]) == 25
  assert diffHighestLowest([5, 5, 5, 5, 5]) == 0
  assert diffHighestLowest([1, 100, 50, -50, 200]) == 250
output: def diffHighestLowest(lst):
      return max(lst) - min(lst)