Problem $2\mathrm{.}11.$

A trader buys two July futures contracts on frozen orange juice. Each contract is for the delivery of $15,000$ pounds. The current futures price is $120$ cents per pound, the initial margin is $$6,000$ per contract, and the maintenance margin is $$4,500$ per contract. What price change would lead to a margin call? Under what circumstances could $$2,000$ be withdrawn from the margin account?

comment: And does a margin call occur when the futures price of frozen orange juice falls to how much per pound?