Which of the following is least soluble in water?

The required amount of $KBr$ (molar mass $= 119 \ g/mol$) in grams to start the precipitation of $AgBr$ in $500 \ mL$ solution of $0.05 \ M \ AgNO_3$ will be :- ($K_{SP}$ of $AgBr = 5 \times 10^{-13}$)

How many grams of $CaC_2O_4$ (molecular mass $= 128$) on dissolving in one litre distilled water will give a saturated solution (in $g$)? $[K_{sp}(CaC_2O_4) = 2.5 \times 10^{-9} \ mol^2 \ L^{-2}]$

The solubility of $BaSO_4$ in pure water (in $g \, L^{-1}$) is closest to
[Given: $K_{sp}$ for $BaSO_4$ is $1.0 \times 10^{-10}$ at $25^{\circ} C$. Molecular weight of $BaSO_4$ is $233 \, g \, mol^{-1}$]

The solubility of $AgBr$ with solubility product $5.0 \times 10^{-13}$ at $298 \ K$ in $0.1 \ M$ $NaBr$ solution would be:

Silver ions are added to a solution with $[Br^{-}] = [Cl^{-}] = [CO_3^{2-}] = [AsO_4^{3-}] = 0.1 \ M$. Which compound will precipitate with the lowest $[Ag^{+}]$ concentration?