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Because they borrow at base rate plus 1.5% which is 2.2 + 1.5 = 3.7%. Interest rates are always quoted as yearly rates, so it is 3.7% per year. However they are borrowing for 4 months, and so they will pay interest of 3.7% x 4/12, which is the same as 3.7/3 You should watch my free lectures on money market hedging and the fact that it is the relative interest rates that determine the forward rate (as per the interest rate formula given on the formula sheet) :-)