<p>In a hydraulic lift, the surface area of the input piston is 6&nbsp;<span class="equation">\(cm^2\)</span>&nbsp;and that of the output piston is 1500&nbsp;<span class="equation">\(cm^2\)</span>. If 100 N ​​​​​​​force is applied to the input piston to raise the output piston by 20 cm, then the work done is _______ kJ.</p>