Consider a portfolio with a current market value of $15,000,000 and duration of 5 years Suppose that the dollar duration of the 10- year Treasury note futures contract is $8,000 How many 10-year futures contracts would you buy/sell to obtain a portfolio duration of 4 years? Round your answer to the nearest whole number [Hint: Calculate the difference between the dollar duration of the target portfolio and the dollar duration of the current portfolio, then divide by the dollar duration of the futures contract. Enter a negative sign if opening a sell' contract, a positive sign if opening a 'buy' contract.]