how to get the correct number? is it (81.48-81.51)/81.51*360/30?

Use the following spot and forward bid-ask rates for the Japanese yen/U.S. dollar (yen/$) exchange rate from September 16, 2010, to answer the following questions: What is the mid-rate quote for each maturity? What is the annual forward premium on the yen for all maturities? (Assume that the U.S. dollar is the home currency.) Which maturities have the smallest and largest forward premiums? (Click on the o icon to import the table into a spreadsheet.) Calculate the annual forward premium for all maturities below: (Round to three decimal places.)