Two masters work together to process a batch of parts. Master Zhang processed all (2/5) in 4 hours, and Master Li processed 280 parts in 4 hours. At this time, the ratio of the number of unprocessed parts to the total number of parts in this batch is 1 : 4. How many parts are there in this batch?
两位师傅共同加工一批零件，张师傅4小时加工了全部的(2/5)，李师傅4小时加工了280个，这时剩下未加工的个数与这批零件总数的比是1：4，这批零件共有多少个？
<gadget id="calculator">2 / 5</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">1 / 4</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">1 - (2/5) - (1/4)</gadget>
<output>7/20 = around 0.35</output>

<gadget id="calculator">280 / (7/20)</gadget>
<output>800</output>

<result>800</result>