Say on May $30,$ you buy $2$ futures contract on gold when the price is $$1400/$oz$.$ and each contract is for $100$ oz$.$ You post $$7000$ in margin for each contract. In the next four days, the following futures prices are observed: $$1397,$ $$1396\mathrm{.}10,$ $$1395\mathrm{.}45,$ $$1380($all stated per oz$.)$