input: Write a python function to assign the value of c to b if a is less than 20.
  assert assign_values(15, 5, 10) == (10, 10)
  assert assign_values(25, 5, 10) == (5, 10)
  assert assign_values(19, 7, 3) == (3, 3)
output: def assign_values(a, b, c):
      if a < 20:
          b = c
      return b, c