Xiaogang's mother earns 2,400 yuan a month. According to the tax law, after deducting 1,600 yuan from the monthly wages, personal income tax is paid on 5% of the balance. How much tax should Xiaogang's mother pay each month?
小刚的妈妈每月工资2400元，按税法规定，每月工资扣除1600元以后，按余额的5%交纳个人所得税，小刚的妈妈每月应上缴税金多少元．
<gadget id="calculator">2_400 - 1_600</gadget>
<output>800</output>

<gadget id="calculator">5 / 100</gadget>
<output>1/20 = around 0.05</output>

<gadget id="calculator">800 * (1/20)</gadget>
<output>40</output>

<result>40</result>