For a manuscript, it takes 5 hours for A to enter alone, and 4 hours for B to enter alone. This manuscript is first entered by A for 2 hours, and how long will it take for the remaining two to record it together?
一份稿件，甲单独录入需5小时完成，乙单独录入需4小时完成．这份稿件先由甲录入2小时后，剩下的两人合录，还需多长时间才能录完？
<gadget id="calculator">1 / 5</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">(1/5) * 2</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 / 4</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">(1/5) + (1/4)</gadget>
<output>9/20 = around 0.45</output>

<gadget id="calculator">(3/5) / (9/20)</gadget>
<output>4/3 = around 1.333333</output>

<result>4/3 = around 1.333333</result>