the monthly payment that amortizes a loan of A dollars in t yr when the interest rate is r per year, compounded monthly, is given by

P=f(A,r,t) = Ar/ 12[1-(1+ r/12)^-12t ]
Find the monthly payment for a home mortgage of 300,000 that will be amortized over 30 yr with an interest rate of 6%/year? And interest rate of 8%/year?