Suppose that you long a gold futures contract in September this year. The maturity month of the contract is on July 2019. Let the gold futures price be $317.50 per ounce in September 2018 and each gold futures contact has 100 ounces. Suppose the initial margin for the futures position is 30% of the initial contract value, the maintenance margin is $100 less than the initial margin. Let the futures price fall with $12.50/per ounce per week since September 1^st.,

a) How much have you deposited cumulatively in maintaining your futures account until today? Show this in details on the weekly basis until the end of November 2018.

b) Suppose the spot price today is $298.05 per ounce, does this show an arbitrage opportunity for you if the risk-free interest rate is 3%?