find %mass

a 50 g sample of solution of naphthalene (C10H8) in benzene (l) has a Tf=4.450C. Calculate the % mass of C10H8 and the boiling point of this solution. (Tf0(benzene)=5.530C, Tb0(benzene)=80.080C, Kf(benzene)=5.120C/m, Kb(benzene)=2.530 C.kg.mol-1)