input: def averageMatrix(matrix):
      sum = 0
      for row in matrix:
          for e in row:
              sum += e
  
      return sum / (len(matrix) * len(matrix[0]))
  
  """
  Calculate the average of elements in a 2-dimensional array.
  >>> averageMatrix([[3,2,6], [8,5,9], [4,7,1]])
  4.777777777777778
  """
output:     count = len(matrix) * len(matrix[0])
      return sum / count