input: Write a python function to compute the weighted average of a list of values and weights.
  assert weightedAverage([90, 50, 70], [0.4, 0.2, 0.4]) == 70.0
  assert weightedAverage([10, 20, 30], [0.2, 0.3, 0.5]) == 23.0
  assert weightedAverage([1, 2, 3], [0.1, 0.2, 0.7]) == 2.6
output: def weightedAverage(values, weights):
      weighted_sum = sum(v * w for v, w in zip(values, weights))
      total_weight = sum(weights)
      return weighted_sum / total_weight