Stephen has just purchased a home for $$$$122$ comma $600.$ A mortgage company has approved his loan application for a$30-$year fixed$-$rate loan at $4\mathrm{.}75\%.$ Stephen has agreed to pay $25\%$ of the purchase price as a down payment. If Stephen made the same loan for $20$ years, how much interest would he$$ save?

monthly payment of principal and interest per$$ $$1,000$ of the amount financed. $5\mathrm{.}22$ annual intrest rate