Dafuyuan Shopping Center held a yogurt promotion of "buy three get one free". The original price was 3.6 yuan per box. Xiaofang bought 12 boxes of this yogurt in total. How much is each box cheaper?
大福源商场举行酸奶"买三送一"的促销活动，原价每盒3.6元，小方一共买了12盒这样的酸奶，实际每盒便宜了多少钱？
<gadget id="calculator">3 + 1</gadget>
<output>4</output>

<gadget id="calculator">3.6 / 4</gadget>
<output>0.9</output>

<result>0.9</result>