It takes 10 hours for Mr. Wang to type a manuscript alone, and 15 hours for Mr. Zhang to type alone. Now they are typing together. After typing, Mr. Wang typed 3,600 more words than Mr. Zhang. How many words are there in this manuscript?
打一份稿件，王老师单独打需要10小时，张老师单独打需要15小时，现在两人合打，打完后王老师比张老师多打3600个字，这份稿件一共有多少个字？
<gadget id="calculator">3 + 2</gadget>
<output>5</output>

<gadget id="calculator">3 / 5</gadget>
<output>3/5 = around 0.6</output>

<gadget id="calculator">2 / 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">3_600 / (1/5)</gadget>
<output>18_000</output>

<result>18_000</result>