The dissolution equilibrium of copper$($I$)$ bromide $(CuBr)$ in water at constant temperature has $K_{sp}=2\mathrm{.}5{10}^{-9}.$

Consider a $500\mathrm{.}0mL$ sample of a $3\mathrm{.}8{10}^{-5}MCuN{O}_3($soluble salt$)$ aqueous solution. Assuming the volume of the solution remains constant,

calculate the minimum mass $($in $m{g}_{?})$ of NaBr$(M_M=102\mathrm{.}894\frac{g}{\text{m}\text{o}\text{l}})$ that must be added to this solution to initiate the spontaneous precipitation of

CuBr.

Report your answer to two significant figures in decimal form without the unit. Example: $9\mathrm{.}0$