and B are 2000m apart. They want to meet at a place, so they walk towards each other at the same time until they meet. A's speed is 60m per minute and B's speed is 40m per minute. A has a dog, and he lets the dog pass the message. The dog starts with A and runs 120m per minute. When it encounters B, it immediately turns around and runs to A, and when it encounters A, it immediately turns around and runs to B. Run back and forth in this way until A and B meet. How many meters did the dog run in total?
甲和乙相距2000m，他们想约个地点见面，于是他们同时相向而行，直到相遇为止．甲的速度是每分钟60m，乙的速度是每分钟40m．甲有一条狗，他就让狗传递信息．狗与甲一起出发，每分钟跑120m，碰到乙的时候立即掉头跑向甲，碰到甲后，又立即调头跑向乙．这样往返来回跑，直到甲和乙相遇为止．这时狗一共跑了多少米？
<gadget id="calculator">60 + 40</gadget>
<output>100</output>

<gadget id="calculator">2_000 / 100</gadget>
<output>20</output>

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

<result>2_400</result>