Now, since we don't count the solids, we don't count the liquids, but we do count gases and Aqueous compounds. When we determine the KSP or the solubility of bonus constants, we don't count this guy or the other guy. We only count these two guys. So KSP is equal to the concentration of A times the concentration of B. In this problem, we're given some unknown amount of barium sulfate and some unknown amount of water in a cup. Now, we want to mix the two and wait for dynamic equilibrium to establish.