A trader named Carlos sells two December futures contracts on Bitcoin. Each contract is for delivery of 5 bitcoins. The current futures price is $31,340 per bitcoin, the initial margin is $300,000 per contract, and the maintenance margin is $200,000 per contract (or $40,000 per bitcoin). Whats the futures price that would lead to a margin call? Under what circumstances could $240,000 be withdrawn from the margin account?