Anyone want to lend a hand on this?

A water trough is 10 m long and a cross section has the shape of an isocelese trapezoid that has a base of 30 cm and a height of 50 cm and is 80 cm wide at the top. If it is being filled with water at a rate of 0.2 m^3 / minute how fast is it rising when the water is 30 cm deep...

I'm not sure what i'm doing on this one. Any help would be great.