Volume · Superchallenge problem

A tank has a floor $25$ cm long and $20$ cm wide. A solid brick $10$ cm long, $10$ cm wide and $20$ cm tall stands upright on the floor of the tank. Water is poured in until it is $12$ cm deep. Then the brick is lifted straight out, without spilling any water. How deep is the water now, in cm? Give your answer as a decimal.