$($Future value of an annuity$)$ Find the future value at the end of year $8$ of an annuity that pays $$3,500$ per year for $8$ years compounded annually at $7$ percent. What would be the future value of this annuity if it were compounded annually at $15$ percent?

a$.$ What would be the future value of this annuity if it were compounded annually at $7$ percent?