In October 2004, the National Bank began to raise interest rates. The regular annual interest rate for one year before the interest rate hike was 1.98%. , and 20% interest tax must be paid before and after the interest rate increase. What is the regular annual interest rate for one year after the interest rate increase?
公元2004年10月，国家银行开始加息，息前一年定期的年利率为1.98%，加息后若把10000元以一年定期存入银行，则比加息前的利息多了21.6元，且加息前后都要上缴20%的利息德税，加息后一年定期的年利率为多少．
<gadget id="calculator">1.98 / 100</gadget>
<output>0.0198</output>

<gadget id="calculator">10_000 * 0.0198</gadget>
<output>198</output>

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

<gadget id="calculator">10_000 * 0.0198 * (1/5)</gadget>
<output>39.6</output>

<gadget id="calculator">21.6 - 39.6</gadget>
<output>-18</output>

<gadget id="calculator">198 + (-18)</gadget>
<output>180</output>

<gadget id="calculator">10_000 * (1/5)</gadget>
<output>2_000</output>

<gadget id="calculator">10_000 - 2_000</gadget>
<output>8_000</output>

<gadget id="calculator">180 / 8_000</gadget>
<output>9/400 = around 0.0225</output>

<result>9/400 = around 0.0225</result>