A and B work together to clean up the snow on the 400-meter circular runway. They walk back to each other from the same place at the same time to clean up. At first, A's cleaning speed is faster than B's (1/3), and then B spent 10 minutes I went to change the tools and came back to continue cleaning, but the work efficiency was doubled compared to the original one. As a result, counting from when A and B started cleaning, after one hour, the work of clearing the snow was completed, and the runway they cleaned was the same length. How many minutes did B work after changing the tool?
甲、乙两人合作清理400米环形跑道上的积雪，两人同时从同一地点背向而行各自进行清理，最初甲清理的速度比乙快(1/3)，后来乙用了10分钟去调换工具，回来继续清理，但工作效率比原来提高了一倍，结果从甲、乙开始清理时算起，经过1小时，就完成了清理积雪工作，并且两人清理的跑道一样长，问乙换工具后又工作了多少分钟？
<gadget id="calculator">10 * 2.5</gadget>
<output>25</output>

<gadget id="calculator">400 / 2</gadget>
<output>200</output>

<gadget id="calculator">60 * 2.5</gadget>
<output>150</output>

<gadget id="calculator">200 - 150</gadget>
<output>50</output>

<gadget id="calculator">25 + 50</gadget>
<output>75</output>

<gadget id="calculator">2.5 - 2.5</gadget>
<output>0</output>

<gadget id="calculator">2.5 + 0</gadget>
<output>2.5</output>

<gadget id="calculator">75 / 2.5</gadget>
<output>30</output>

<result>30</result>