A solution containing 10g dm3 of urea( mol. mass =60) is isotonic with a 5% solution of non volatile solute. the molecular mass of this non volatile solute is 

a) 250g/mol

b) 300 g/mol

c) 350 g/mol

d) 200 g/mol

 sir i am not able to figure out the mass of the nonvolatile solute ,pls help