$13)\_\_\_\_\_$At $8$ percent compounded annually, how long will it take $$57,900$ to double?a$.3$ yearsb. $11$ yearsc. $8$ yearsd $9$ years

$14)\_\_\_\_\_\_$How much must be invested today in order to generate a ten$-$year annual annuity of $$9,300$ per year, with the first payment one year from today, at an interest rate of $6\%?$a$.$ $$74,876$b$.$ $$68,449$c$.$ $$7,863\mathrm{.}21$d$.$ $$32,498$

$15)\_\_\_\_\_\_\_$A bank offers to loan you $$31,550$ for six years to buy a car. The loan shall be paid back in $72$ monthly payments. The interest rate offered on the loan is $4\mathrm{.}70\%$ compounded monthly. What monthly payment should you expect on the loan?a$.$ $$551\mathrm{.}28$b$.$ $$587\mathrm{.}43$c$.$ $$503\mathrm{.}73$d$.$ $$559\mathrm{.}32$