input: Write a python function to find the minimum, maximum, and average of a list of numbers.
  assert find_min_max_avg([1, 2, 3, 4, 5]) == 3
  assert find_min_max_avg([10, 20, 30, 40, 50]) == 30
  assert find_min_max_avg([5, 10, 15, 20, 25]) == 15
output: def find_min_max_avg(nums):
      if not nums:
          return None
      minimum = min(nums)
      maximum = max(nums)
      average = sum(nums) / len(nums)
      return (minimum, maximum, average)