A shopping mall holds a sales promotion. Buy one item and sell it at 90% of the original price, and buy two items and sell it at 70% of the original price. The original price of a coat is 400 yuan. How much more will you pay if you buy two coats instead of one?
某商场举行促销活动，同一种商品，买一件按原价的90%出售，买两件按原价的70%出售．一件外套原价400元，买两件比买一件只需多付多少元？
<gadget id="calculator">70 / 100</gadget>
<output>7/10 = around 0.7</output>

<gadget id="calculator">400 * (7/10) * 2</gadget>
<output>560</output>

<gadget id="calculator">90 / 100</gadget>
<output>9/10 = around 0.9</output>

<gadget id="calculator">400 * (9/10)</gadget>
<output>360</output>

<gadget id="calculator">560 - 360</gadget>
<output>200</output>

<result>200</result>