Some amount of dichloromethane ($\mathrm{CH}_2 \mathrm{Cl}_2$) is added to 671.141 mL of chloroform ($\mathrm{CH} \mathrm{Cl}_3$) to prepare 2.6 × 10–3M solution of $\mathrm{CH}_2 \mathrm{Cl}_2$ (DCM). The concentration of DCM is ______ ppm (by mass). Given: Atomic mass : C = 12; H : 1; Cl = 35.5 density of CHCl3 = 1.49g c $\mathrm{cm}^{-3}$