There is a pool with two water inlet pipes, A and B. Both pipes are open at the same time, and the pool can be filled in 10 minutes. If pipe A is opened alone, the pool can be filled in 14 minutes. If both pipes are open at the same time, after 4 minutes, close pipe A and pipe B. How many more minutes will it take to fill this pool if the pipe remains open?
有一个水池，装有甲乙两个进水管，两管同时开放，10分钟可以灌满水池，单开甲管，14分钟可以灌满水池，如果两管同时开放4分钟后，关闭甲管，乙管继续开放，还需几分钟才能灌满这一水池？
<gadget id="calculator">1 / 10</gadget>
<output>1/10 = around 0.1</output>

<gadget id="calculator">(1/10) * 4</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">1 - (2/5)</gadget>
<output>3/5 = around 0.6</output>

<gadget id="calculator">1 / 14</gadget>
<output>1/14 = around 0.071429</output>

<gadget id="calculator">(1/10) - (1/14)</gadget>
<output>1/35 = around 0.028571</output>

<gadget id="calculator">(3/5) / (1/35)</gadget>
<output>21</output>

<result>21</result>