2. (2 points) Calculate the difference between the present value of $300 per year cash payments for the next 40 years and the present value of $300 per year cash payments in perpetuity. Assume in either case, the first payment occurs one year from today and that the appropriate discount rate is 10%/year. The difference in the present value of these two streams of future cash payments that you calculated equals the present value of cash payments over what period of time