Select 4 people from 10 boys and 10 girls to participate in the sports meeting. It is required to include at least 1 boy and 1 girl. How many ways are there to choose?
从10名男生和10名女生中选出4人参加运动会，要求至少包含1个男生和1个女生，有多少种选法？
<gadget id="calculator">20 * 19 * 18 * 17</gadget>
<output>116_280</output>

<gadget id="calculator">4 * 3 * 2 * 1</gadget>
<output>24</output>

<gadget id="calculator">116_280 / 24</gadget>
<output>4_845</output>

<gadget id="calculator">10 * 9 * 8 * 7</gadget>
<output>5_040</output>

<gadget id="calculator">5_040 / 24</gadget>
<output>210</output>

<gadget id="calculator">210 * 2</gadget>
<output>420</output>

<gadget id="calculator">4_845 - 420</gadget>
<output>4_425</output>

<result>4_425</result>