At first, it turns out convenient to compute the total moles of sodium that will be dissolved into the solution by considering the added amounts of sodium bromide and sodium sulfate:
Once we've got the moles we compute the final volume via:
Thus, the molarity of the sodium atoms turn out into:
Now, we perform the same procedure but now for the bromide ions:
Ionic (or electrovalent) compounds conduct electricity when there they are in the aqueous state/solution because the charges of ions of these compounds are what carry the electric charges in the aqueous solution as a result of free movement within the aqueous solution which they do not "have" when in there solid state (where they have a highly restricted movement/compacted structure).
Stirring affects how quickly a solute dissolves in a solvent, but has no effect on how much solute will dissolve. The amount of solute that will dissolve is affected by temperature - more will dissolve at higher temperatures. This is called the solubility of the solute