The charging standard of a certain express company is: less than 3kg (including 3kg) will be charged 15 yuan, and when it exceeds 3kg, the price will be increased by 2.4 yuan for each additional 1kg, and the price of less than 1kg will be calculated as 1kg. How much does Uncle Liu need to pay for sending 12kg?
某快递公司的收费标准是：低于3kg(包含3kg)一律收15元，超出3kg时，每增加1kg加价2.4元，不到1kg的按1kg计算．刘叔叔要寄12kg的东西，需要付费多少元？
<gadget id="calculator">12 - 3</gadget>
<output>9</output>

<gadget id="calculator">9 * 2.4</gadget>
<output>21.6</output>

<gadget id="calculator">21.6 + 15</gadget>
<output>36.6</output>

<result>36.6</result>