A water tank of dimensions 20 cm x 5 cm x 10 cm has 307 cc water in it. A few bricks, each of dimensions 5 cm x 2 cm x 1 cm are fully submerged in the tank. Each brick absorbs 30% of its own volume of water. Just enough bricks are put in, such that the water level rises to completely fill the tank. How many bricks were put in the tank?