Two engineering teams, A and B, dig a tunnel at the same time from both ends. Team A digs 9 meters every day, and Team B digs 11 meters every day. After 120 days, the tunnel will be finished. What is the length of this tunnel?
甲、乙两个工程队分别从两端同时开凿一条隧道．甲队每天凿9米，乙队每天凿11米，120天后凿完，求这条隧道的长度？
<gadget id="calculator">9 + 11</gadget>
<output>20</output>

<gadget id="calculator">20 * 120</gadget>
<output>2_400</output>

<result>2_400</result>