John has saved $20,000 and he wants to buy a $100,000 house. If he pays just $10,000 as a down payment, he will have a $90,000 mortgage with a monthly payment of $500. If he pays all of his savings ($20,000) as a down payment, he will only have an $80,000 mortgage and a lower interest rate resulting in a $420 monthly payment. He should choose to pay _____.