Two elements A and B form compounds having formula AB2 and AB4. When dissolved in 20 g of benzene (C₆H₆), 1 g of AB2 lowers the freezing point by 2.3 Kwhereas 1.0 g of AB4 lowers it by 1.3 K. The molar depression constant for benzene is 5.1 Kkg mol⁻¹. Calculate atomic masses of A and B.