Boiling Point Elevation Unknown Solute

A solution containing 0.5216 g of napthalene (molecular weight = 128.16) in 50 mL of CCl₄ shows boiling point elevation of 0.402 °C. While a solution of 0.6216 g of an unknown solute in the same weight of solvent gave a boiling point elevation of 0.647 °C. The molecular mass of unknown solute is