A and B have a typing competition. A typed 8400 words and B typed 6600 words in one hour. How many more words does A type than B per minute?
甲、乙两人比赛打字，1小时甲打了8400个字，乙打了6600个字，平均每分钟甲比乙多打多少个字？
<gadget id="calculator">8_400 / 60</gadget>
<output>140</output>

<gadget id="calculator">6_600 / 60</gadget>
<output>110</output>

<gadget id="calculator">140 - 110</gadget>
<output>30</output>

<result>30</result>