How much water is necessary to make a solution with a molality of when of sodium chloride are in the solution?

Consider the reaction of potassium carbonate with calcium nitrate to form potassium nitrate and calcium carbonate:

Suppose 50ml of a 0.250M potassium carbonate solution was mixed with 100ml of a 0.175M calcium nitrate solution. What is the maximum amount of calcium carbonate that could be obtained?

What is the mass of the solid left over after boiling off 100mL of 0.4M NaCl solution?