Taryn Arsenault is a regular commodities speculator. She is currently considering a short position in July oats, which are now trading at 248. Her analysis suggests that July oats, should be trading at about 240 in a couple of months. Assuming that her expectations hold up, what kind of return on invested capital will she make if she shorts 3 July oats contracts (each contract covers 5000 bushels of oats) by depositing an initial margin of $540 per contract? Her return on invested capital is __ %?