input: def runningTotal(arr):
      """
      Compute the running total of numbers in a given list using numpy.
      
      >>> runningTotal([1, 2, 3, 4])
      array([ 1,  3,  6, 10])
      >>> runningTotal([5, 10, 15, 20])
      array([ 5, 15, 30, 50])
      """
      return np.cumsum(arr)
output:     import numpy as np