The World Trade Center has 4 floors underground and 20 floors on the ground. It takes 20 seconds for the elevator to go from the 1st floor to the 5th floor. How many seconds does it take for Manager Wang to take the elevator from the 15th floor above the ground to the 4th floor underground?
世贸大厦地下有4层，地上有20层，电梯从1层到5层需要20秒钟，那么王经理乘坐电梯从地上15层到地下4层，需要多少秒．
<gadget id="calculator">5 - 1</gadget>
<output>4</output>

<gadget id="calculator">20 / 4</gadget>
<output>5</output>

<gadget id="calculator">15 - 1</gadget>
<output>14</output>

<gadget id="calculator">14 + 4</gadget>
<output>18</output>

<gadget id="calculator">5 * 18</gadget>
<output>90</output>

<result>90</result>