With the four numbers 9, 8, 7, and 6, many four-digit numbers without repeated numbers can be formed. What is the sum of all these four-digit numbers?
用9、8、7、6这四个数可以组成许多没有重复数字的四位数，所有这些四位数的和是多少．
<gadget id="calculator">1 / 4</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">4 * 3 * 2 * (1/4)</gadget>
<output>6</output>

<gadget id="calculator">9 + 8 + 7 + 6</gadget>
<output>30</output>

<gadget id="calculator">1_000 + 100 + 10 + 1</gadget>
<output>1_111</output>

<gadget id="calculator">30 * 4 * 3 * 2 * (1/4) * 1_111</gadget>
<output>199_980</output>

<result>199_980</result>