There are 500 parts, and after A and B cooperate for 4 days, there are still 20 left. A makes 75 per day, how many does B produce per day?
有500个零件，甲、乙合作4天后还剩20个．甲每天做75个，乙每天生产多少个？
<gadget id="calculator">75 * 4</gadget>
<output>300</output>

<gadget id="calculator">500 - 40 - 300</gadget>
<output>160</output>

<gadget id="calculator">160 / 4</gadget>
<output>40</output>

<result>40</result>