The price of Qintang Maojian tea is 160 yuan per 500 grams. During the "May 1st" period, promotional activities will be held, and 0.1 kg will be given away for every 500 grams purchased. Teacher Li wants to buy 2.5 kilograms of tea leaves, how much should he pay?
覃塘毛尖茶每500克售价160元，"五一"期间搞促销活动，每购买500克赠送0.1千克．李老师要买2.5千克茶叶，应付多少元？
<gadget id="calculator">160 / 0.5</gadget>
<output>320</output>

<gadget id="calculator">2 / 0.5</gadget>
<output>4</output>

<gadget id="calculator">0.1 * 4</gadget>
<output>0.4</output>

<gadget id="calculator">2.5 - 0.4</gadget>
<output>2.1</output>

<gadget id="calculator">320 * 2.1</gadget>
<output>672</output>

<result>672</result>