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. Once equilibrium establishes, we're given that the KSP or the Solubility product is equal to 1.0 times ten to negative ten at 25 degrees Celsius. So we want to find the solubility of barium sulfate. To find the solubility of barium sulfate, we must first write the dissociation reaction for barium sulfate.