I could be wrong, but I think your cash balance more than covers it. Full value is 1500 plus you need an additional half of that which would be 750 - that is under your 3k cash amount. If it goes down your full margin amount - the 6k will be the broker's collateral. But when and if they give you a margin call I am not sure. If I were you I would get on the phone with your broker - or better yet, email them this way you have your explanation in writing.
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