Dad deposits 20,000 yuan in the bank for one year, with an annual interest rate of 3.06%. Donate the after-tax interest to the "Hope Project" when the plan expires. Interest tax is 20%, how much can dad donate?
爸爸将20000元存入银行，定期一年，年利率是3.06%．准备到期后把税后利息捐给"希望工程"．利息税是20%，爸爸能捐款多少元？
<gadget id="calculator">3.06 / 100</gadget>
<output>0.0306</output>

<gadget id="calculator">20 / 100</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">1 - (1/5)</gadget>
<output>4/5 = around 0.8</output>

<gadget id="calculator">20_000 * 0.0306 * 1 * (4/5)</gadget>
<output>489.6</output>

<result>489.6</result>