The solubility product of calcium oxalate is `2 xx 10^(–9)` at `25^@C`. Calculate the solubility of calcium oxalate at this temperature. What will be its solubility in a 0.1 M solution of ammonium oxalate ? Assume that ammonium oxalate is completely ionized in solution. Name the effect, which operates on addition of ammonium oxalate to calcium oxalate.