It takes 10 days for A to print a manuscript alone, 5 days for B to print alone, and 4 days for A to print and the remaining two to finish it together. How many days will it take to print this manuscript?
一份稿件甲单独打需要10天完成，乙单独打印5天完成，甲打印4天后余下的二人合作完成，打印这份稿件还需要几天？
<gadget id="calculator">1 / 10</gadget>
<output>1/10 = around 0.1</output>

<gadget id="calculator">(1/10) * 4</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">1 - (2/5)</gadget>
<output>3/5 = around 0.6</output>

<gadget id="calculator">1 / 5</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">(1/10) + (1/5)</gadget>
<output>3/10 = around 0.3</output>

<gadget id="calculator">(3/5) / (3/10)</gadget>
<output>2</output>

<result>2</result>