input: from typing import List
  
  
  def min_max(arr: List[float]) -> List[float]:
      """ Given an array of numbers, return an array with the greatest and smallest values.
      >>> min_max([3, 4, 2, 8, 15, 6])
      [2, 15]
      >>> min_max([7, -1, -3, 0, 5])
      [-3, 7]
      """
output:     min_val = min(arr)
      max_val = max(arr)
      return [min_val, max_val]