input: Write a function to return an array with the running total of numbers in a given list using numpy. 
  assert np.array_equal(runningTotal([1, 2, 3, 4]), np.array([1, 3, 6, 10]))
  assert np.array_equal(runningTotal([0, 0, 0, 0]), np.array([0, 0, 0, 0]))
  assert np.array_equal(runningTotal([-1, 2, -3, 4]), np.array([-1, 1, -2, 2]))
  assert np.array_equal(runningTotal([]), np.array([]))
  assert np.array_equal(runningTotal([1]), np.array([1]))
output: import numpy as np
  
  def runningTotal(arr):
      return np.cumsum(arr)