There is a batch of materials to be copied, which can be completed in 11 hours by machine A alone or by machine B in 13 hours. When both machines A and B make copies at the same time, due to mutual interference, the two machines print less than 28 sheets per hour. Now it takes 6 hours for the two machines to copy at the same time. How many sheets are there in this batch of data?
有一批资料要复印，甲机独印11小时或乙机独印13小时可完成，当甲、乙机同时复印，因相互干扰，每小时两台共少印28张．现在两机同时复印用了6小时印完．则这批资料共有多少张．
<gadget id="calculator">1 / 11</gadget>
<output>1/11 = around 0.090909</output>

<gadget id="calculator">1 / 13</gadget>
<output>1/13 = around 0.076923</output>

<gadget id="calculator">1 / 6</gadget>
<output>1/6 = around 0.166667</output>

<gadget id="calculator">(1/13) - (1/6)</gadget>
<output>-7/78 = around -0.089744</output>

<gadget id="calculator">(1/11) + (-7/78)</gadget>
<output>1/858 = around 0.001166</output>

<gadget id="calculator">28 / (1/858)</gadget>
<output>24_024</output>

<result>24_024</result>