<p>A plane is in level flight at constant speed and each of its two wings has an area of 40&nbsp;<span class="equation">\(m^2\)</span>.&nbsp;If the speed of the air is&nbsp; 180 km/h over the lower wing surface and&nbsp; 252 km/h over the upper wing surface, the mass of the plane is ___________ kg.</p>

<p>(Take air density to be 1 kg&nbsp;<span class="equation">\(m^{-3}\)</span>&nbsp;and g = 10&nbsp;<span class="equation">\(ms^{-2}\)</span>)​​​​​​​</p>