input: Write a function to calculate the running total of numbers in a given list using numpy. Return the array with the running total. 
  
  Assert examples:
  assert np.array_equal(runningTotal([1, 2, 3, 4]), np.array([1, 3, 6, 10]))
  assert np.array_equal(runningTotal([5, 10, 15, 20]), np.array([5, 15, 30, 50]))
  assert np.array_equal(runningTotal([]), np.array([]))
output: import numpy as np
  
  def runningTotal(numbers):
      return np.cumsum(numbers)