input: Write a function to calculate the average of elements in a 2-dimensional array. Return the result rounded to two decimal places.
  
  ### Function Definition:
  def averageMatrix(matrix):
   sum = 0
   for row in matrix:
    for e in row:
     sum += e
  
   return round(sum / (len(matrix) * len(matrix[0])), 2)
  
  ### Test Cases:
  a = [[3,2,6],
       [8,5,9],
       [4,7,1]]
  
  assert averageMatrix(a) == 5.0
  assert averageMatrix([[1,2],[3,4]]) == 2.5
  assert averageMatrix([[10,20],[30,40]]) == 25.0
  assert averageMatrix([[1,1],[1,1]]) == 1.0
  assert averageMatrix([[]]) == 0.0
output: def averageMatrix(matrix):
      if not matrix or not matrix[0]:
          return 0.0
      sum = 0
      for row in matrix:
          for e in row:
              sum += e
      return round(sum / (len(matrix) * len(matrix[0])), 2)