Uncle Li plans to deposit 50,000 yuan in the bank for a period of one year, and donate the after-tax interest to the Hope Project after the maturity date. The annual interest rate is 2.25%, and the interest tax is 20%. How much can Uncle Li donate?
李伯伯计划将5万元存入银行，定期一年，到期后将税后利息捐给希望工程，年利率是2.25%，利息税是20%．李伯伯可捐款多少元？
<gadget id="calculator">5 * 10_000</gadget>
<output>50_000</output>

<gadget id="calculator">2.25 / 100</gadget>
<output>0.0225</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">50_000 * 0.0225 * 1 * (4/5)</gadget>
<output>900</output>

<result>900</result>