The big bell in the school bell tower rings 3 times at 3 o'clock, and it takes 4 seconds to finish. How many seconds does it take to ring 6 times at 6 o'clock?
学校钟楼的大钟3时敲响3下，4秒钟敲完．6时敲响6下需要多少秒．
<gadget id="calculator">6 - 1</gadget>
<output>5</output>

<gadget id="calculator">3 - 1</gadget>
<output>2</output>

<gadget id="calculator">4 / 2</gadget>
<output>2</output>

<gadget id="calculator">5 * 2</gadget>
<output>10</output>

<result>10</result>