Assume that the margin requirement on the CSI300 futures contract is 10%, and the stock index future is settled in May 20, 2019 at 3,000.

a) How much margin must be put up for holding each contract?

b) Investor A shorted one contract in May 21 at 3,000. If the futures price settled at 3,020 in May 21, what will happen to the margin account of investor A at market close of May 21?

c) What was the investor As percentage return based on the amount put up as margin in May 21 after market close?

d) Investor B sent $ 200,000 to setup her margin account with her broker in May 19, and longed two CSI300 index contracts in May 20 at 3000. In May 21, investor B closed one contract at 3,020. In May 22, investor B did nothing while the futures price settled at 2,960. What was the investor Bs percentage total investment return up to May 22 after market close?