input: Write a python function to implement functionA that returns the sum of two numbers and functionB that returns the product of two numbers.
  assert functionA(3, 5) == 8
  assert functionA(10, 15) == 25
  assert functionB(3, 5) == 15
  assert functionB(4, 7) == 28
output: def functionA(a, b):
      return a + b
  
  def functionB(a, b):
      return a * b