2. The maturity of the cheapest to deliver is the shortest maturity of all deliverable bonds if the market interest rate is less than 8 percent. If the market interest rate is greater than 8 percent, the maturity of the CTD is the largest deliverable maturity if the optimal coupon is greater than 8 percent; if the optimal coupon is less than 8 percent, then there is the possibility of an optimal deliverable maturity which is neither the largest nor the smallest deliverable maturity (an interior optimum).