Two small boats keep a distance of 600 meters from the upstream of the river to the downstream, and two people A and B are at the same place on the river bank. When the boat in front comes in front of the two people, A goes upstream and B goes downstream at the same speed. In this way, A met the boat behind after two minutes, and after another 3 minutes, B was overtaken by the boat behind. Ask how fast the two of them are walking?
两艘小船保持600米的间隔从河的上游往下游开，两个人A和B在河岸上同一地点．当前面的小船来到两个人的面前时，A向河的上游，B向河的下游以相同的速度走出去．这样，A在两分钟后遇上了后面的小船，又过了3分钟，B被后面的小船超过．问他们两人行走的速度是多少？
<gadget id="calculator">2 + 3</gadget>
<output>5</output>

<gadget id="calculator">600 / 5</gadget>
<output>120</output>

<gadget id="calculator">120 * 2</gadget>
<output>240</output>

<gadget id="calculator">600 - 240</gadget>
<output>360</output>

<gadget id="calculator">2 + 2</gadget>
<output>4</output>

<gadget id="calculator">360 / 4</gadget>
<output>90</output>

<result>90</result>