You took out a $30-$year fixed$-$rate mortgage for $$700,000$ with an interest rate of $7\mathrm{.}2\%($APR$).$ a$)$ What is the monthly payment? b$)$ What is the outstanding balance on your mortgage after $20$ years? c$)20$ years after you took out the original mortgage, interest rates have fallen to $4\mathrm{.}8\%.$ What is your new monthly payment if you refinance your mortgage and get a new $10-$year mortgage? d$)$ What are your monthly savings from refinancing? all asnwers in excel and with functions