A portfolio of bonds has a market value of $300M, and an average duration of 8.3. The manager wants to reduce duration to 5.5. To make the change, the manager will take a position in treasury futures. The futures contracts have a cheapest-to-deliver bond with a duration of 7.0 and an underlying value of $100,000. The conversion factor for the cheapest-to-deliver bond is 1.0. How many contracts does the manager need to short in order to execute the change?