[填空题]
A trough, containing water, of h ll4qif uh 55,c 1d*uhfq6i8wlen4:; c*cmgs btkgth 8 m has a uniform cross-section in the shape of ms; bkc: ct4*ga trapezoid, with side lengths shown below.
When the water is h \mathrm{~m} deep, the volume of water in the trough is given by
$V(h)=16 h+\frac{8 h^{2}}{\sqrt{3}}$
Water leaks from the bottom of the trough at a constant rate of $3.1 \mathrm{~m}^{3}$ per minute. Find the rate at which the height of the water level h is falling at the instant when the water has $50 \mathrm{~cm}$ of depth.
the height of the water level is falling at a rate of cm/min
