Aunt Zhang deposits 20,000 yuan in the bank for 2 years, with an annual interest rate of 3.50%. After the maturity, Aunt Zhang can get how much after-tax interest. (Interest tax is calculated at 5%)
张阿姨把20000元存入银行，定期2年，年利率是3.50%，到期后张阿姨可以得到税后利息多少元．(利息税按5%计算)
<gadget id="calculator">2.5 / 100</gadget>
<output>0.025</output>

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

<gadget id="calculator">1 - (1/20)</gadget>
<output>19/20 = around 0.95</output>

<gadget id="calculator">20_000 * 0.025 * 2 * (19/20)</gadget>
<output>950</output>

<result>950</result>