I need help understanding covered interest arbitrage (CIA).

Takeshi Kamada, a foreign exchange trader at Credit Suisse (Tokyo), is exploring covered interest arbitrage possibilities. He wants to invest $5,000,000 or its yen equivalent, in a covered interest arbitrage between U.S. dollars and Japanese yen. He faced the following exchange rate and interest rate quotes. Is CIA profit possible? If so, how?

Arbitrage funds available $5,000,000

Spot rate (/$) 118.60

180-day forward rate (/$) 117.80

180-day U.S. dollar interest rate 4.800%

180-day Japanese yen interest rate 3.4%

I can set the problem up just fine. My issue is that as I'm going over my professors explanation he used 2.4% for the interest because he says the 4.8% is an annual quote. Why would the question state 180 day (Currency) interest and yet still be annual quote?

Thank you.