Expiration Time	Wheat(cents/bushels)	Corn(cents/bushels)	Soybeans(cents/bushels)
Today=Spot	540	610	1320
6-month	560	600	1350
12-month	590	587	1480
18-month	625	580	1370
24-month	655	570	1265

Risk free interest rate is 4%

a) Given a lease rate of 7.0% on the 24-month corn forward contract, what is the approximate potential arbitrage profit per contract? Answer:4.48 cents

b) The lease rate on the 6-month soybean contract is 0.35%. What is the implied annual storage cost if the cost is continuously paid and proportional? Answer: 0.84%

Please help me with the calculations. Subject is derivatives market