Guoguojia ordered 3 boxes of yogurt every day in July, and paid a total of 316.2 yuan at the preferential price, and each bottle of milk was 4.15 yuan. How much cheaper is each box than the retail price?
果果家7月份每天订3盒酸奶，按优惠价共付316.2元，每瓶牛奶4.15元，这样每盒比零售价便宜多少元？
<gadget id="calculator">3 * 31</gadget>
<output>93</output>

<gadget id="calculator">316.2 / 93</gadget>
<output>3.4</output>

<gadget id="calculator">4.15 - 3.4</gadget>
<output>0.75</output>

<result>0.75</result>