input: Write a function to compute the product of two numbers using both non-recursive and recursive methods.
  assert prod_non_recursive(2, 3) == 8
  assert prod_non_recursive(5, 0) == 1
  assert prod_non_recursive(3, 4) == 81
  assert prod_recursive(2, 3) == 8
  assert prod_recursive(5, 0) == 1
  assert prod_recursive(3, 4) == 81
output: def prod_non_recursive(a, b):
      result = 1
      for _ in range(b):
          result *= a
      return result
  
  def prod_recursive(a, b):
      if b == 0:
          return 1
      return a * prod_recursive(a, b - 1)