9. On August 1 a portfolio manager has a bond portfolio worth $10 million. The duration of the portfolio in October will be 7.1 years. The December Treasury bond futures price is currently 91 -12 and the cheapest-todeliver bond will have a duration of 8.8 years at maturity. Each contract is for the delivery of $100,000 face value of bonds How should the portfolio manager immunize the portfolio against changes in interest rates over the next two months