Consider the valuation of a one-year forward contract on a two-year bond. The two-vear bonds price is 800, the delivery price is 820, and two coupons of 50 will be paid in 6 and 12 months, respectively. The risk-less interest rate is 8% per annum for 6 months and 9% per annurn, for 12 months. In order to apply the formula, the value of l must be discounted to the present at an appropriate interest rate?