You have recently purchased a home and taken out a $$450,000$ twenty $(20)$ year mortgage with an annual nominal or stated interest rate equal to $7\mathrm{.}50\%.$ What is your monthly mortgage payment on this mortgage? How much of your first monthly payment is interest expense and how much of your first monthly payment is principal paydown? $6$b$)$ What would your monthly mortgage payment be if the stated interest rate was $5\mathrm{.}50\%?$