It takes 12 hours for A and B to complete a manuscript, and it takes 20 hours for A to complete it alone. Now, two people work together until the task is completed. A typed 9,000 words more than B. How many thousands of words are there in this manuscript?
一份稿件甲乙合打要12小时完成，甲独打要20小时完成，现由两人合打直至完成任务，甲比乙多打0.9万字．这份稿件共有多少万字？
<gadget id="calculator">1 / 20</gadget>
<output>1/20 = around 0.05</output>

<gadget id="calculator">(1/20) * 12</gadget>
<output>3/5 = around 0.6</output>

<gadget id="calculator">1 - (3/5)</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">(3/5) - (2/5)</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">0.9 / (1/5)</gadget>
<output>4.5</output>

<result>4.5</result>