10 street lamps are installed in sequence on a small street. In order to save electricity and not affect the road lighting, 4 of the 8 lamps except the first and last two lamps should be turned off, but the turned off lamps cannot be adjacent to each other. How many lights are there in total? Different customs.
一条小街上顺次安装10盏路灯，为了节约用电又不影响路面照明，要关闭除首末两灯以外的8盏灯中的4盏灯，但被关的灯不能相邻，共有多少不同的关法．
<gadget id="calculator">5 * 4 * 3 * 2</gadget>
<output>120</output>

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

<gadget id="calculator">120 / 24</gadget>
<output>5</output>

<result>5</result>