#4. If an investment of $800 earned interest of $320 at 6% compounded monthly, for how many years was the money invested? Show all the steps of calculations

#8. Joan borrowed $3000 today with the understanding that she would repay the loan in two payments: $1600 in one year and a second payment of $1700. If interest is 8% compounded quarterly, when should the second payment be made? Show the steps

#12.A contract requires payments of $4000 today, $5000 in three years, and $6000 in five years. When can the contract be fulfilled by a single payment equal to the sum of the required payments if money is worth 9% p.a. compounded monthly? show all the steps