Two people, A and B, are running on a 400-meter circular track. They start from the same place. If they go in the same direction, A will catch up with B in 10 minutes. If they run in the opposite direction, A will meet B in 2 minutes. How many minutes does it take B to complete a lap?
甲、乙两人在400米的环形跑道上跑步，他们从同一地点出发，若同向而行，甲10分钟追上乙，若背向而行，甲2分钟与乙相遇．乙跑完一圈要多少分钟？
<gadget id="calculator">400 / 2</gadget>
<output>200</output>

<gadget id="calculator">400 / 10</gadget>
<output>40</output>

<gadget id="calculator">200 - 40</gadget>
<output>160</output>

<gadget id="calculator">160 / 2</gadget>
<output>80</output>

<gadget id="calculator">400 / 80</gadget>
<output>5</output>

<result>5</result>