Hongguang Printing Factory bound a batch of diaries. A total of 960 diaries were bound in the first three days, and an average of 420 were bound every day in the next six days. How many diaries are there in total?
红光印刷厂装订一批日记本，前三天共装订了960本，后6天平均每天装订420本．这批日记本共有多少本？
<gadget id="calculator">420 * 6</gadget>
<output>2_520</output>

<gadget id="calculator">2_520 + 960</gadget>
<output>3_480</output>

<result>3_480</result>