A and B make 150 parts in total (1/4) hour, A makes 200 parts per hour, how many parts does B make per hour?
甲乙两人(1/4)小时共做150个零件，甲每小时做200个，乙每小时做多少个？
<gadget id="calculator">1 / 4</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">150 / (1/4)</gadget>
<output>600</output>

<gadget id="calculator">600 - 200</gadget>
<output>400</output>

<result>400</result>