Xiao Gang and Xiao Ming talk on the phone. The first three minutes cost 0.20 yuan, and the fourth minute costs 0.10 yuan per minute. They talk for 8 minutes. How much is the average call fee per minute?
小刚和小明通电话，前三分钟需要话费0.20元，第4分钟起每分钟需要话费0.10元，他们通话8分钟，平均每分钟的话费是多少元？
<gadget id="calculator">8 - 3</gadget>
<output>5</output>

<gadget id="calculator">0.1 * 5</gadget>
<output>0.5</output>

<gadget id="calculator">0.2 + 0.5</gadget>
<output>0.7</output>

<gadget id="calculator">0.7 / 8</gadget>
<output>0.0875</output>

<result>0.0875</result>