The taxi fare standard in a certain city is as follows: 5 yuan within 3km; 1.4 yuan per kilometer for more than 3km (less than 1 kilometer is calculated as 1km). Uncle Li takes a taxi to a shopping mall 20km away from home. How much should he pay for the fare?
某市出租车收费标准如下：3km以内5元；超过3km，每千米1.4元(不足1千米按1km计算)，李叔叔乘出租车去离家20km的商城，他应付车费多少元？
<gadget id="calculator">20 - 3</gadget>
<output>17</output>

<gadget id="calculator">1.4 * 17</gadget>
<output>23.8</output>

<gadget id="calculator">23.8 + 5</gadget>
<output>28.8</output>

<result>28.8</result>