As of May 15, the margin balance is $4,650 (see solution to previous question). Since this is below the initial margin of $6,000 (both contracts), but still above the maintenance margin of $3,000, (for both contracts) no action is required.
There are three types of margin. The first deposit is called the initial margin. Initial margin must be posted before any trading takes place. Initial margin is fairly low and equals about one day’s maximum price fluctuation. The margin requirement is low because at the end of every day there is a daily settlement process called marking-the-account-to-market. In marking-to-market, any losses for the day are removed from the trader’s account and any gains are added to the trader’s account. If the margin balance in the trader’s account falls below a certain level (called the maintenance margin), the trader will get a margin call and have to deposit more money (called the variation margin) into the account to bring the account back up to the initial margin level.