A farm raises 840 sheep, of which 560 sheep are improved breeds. On average, each sheep can produce 7.1 kg of wool a year, and the rest of the sheep can produce an average of 6.5 kg of wool a year. How many kilograms of wool can the sheep on this farm produce in a year?
某农场养羊840只，其中560只羊是改良品种，平均每只羊一年可出羊毛7.1千克，其余的平均每只羊一年可出羊毛6.5千克．这个农场的羊一年一共可以出羊毛多少千克？
<gadget id="calculator">7.1 * 560</gadget>
<output>3_976</output>

<gadget id="calculator">840 - 560</gadget>
<output>280</output>

<gadget id="calculator">6.5 * 280</gadget>
<output>1_820</output>

<gadget id="calculator">3_976 + 1_820</gadget>
<output>5_796</output>

<result>5_796</result>