A trough is $6 \mathrm{~m}$ long and its ends have the shape of isosceles triangles that are $1 \mathrm{~m}$ across at the top and have a height of $50 \mathrm{~cm}$. If the trough is being filled with water at a rate of $1.2 \mathrm{~m}^{3} / \mathrm{min}$, how fast is the water level rising when the water is 30 centimeters deep?