Suppose that the effective interest rate per interest period is 6%. Describe what the following annuity symbol (Ds)28) means. o he value at the time of the last payment of an annuity-immediate, where each payment is one less than its predecessor. The value at the time of the first payment of an annuity-immediate, where subsequent payments decrease by 6%. The value at the time of the first payment of a perpetuity-due with payments decreasing by 1 each period. The value at the time of the first payment of an annuity-due, where subsequent payments increase by 6%. The value at the time of the last payment of a perpetuity-due with payments increasing by 1 each period