Assign the CIP descriptors of the two stereocentres of the compound shown, numbering the carbon chain so that the carbon bearing bromine is C-2.

At the bromine-bearing carbon (C-2): $\mathrm{Br}>\mathrm{CHCl}$ (Cl,C,H) $>\mathrm{CH}{}_3>\mathrm{H}$, descriptor R. At the chlorine-bearing carbon (C-3): $\mathrm{Cl}>\mathrm{CHBr}$ (Br,C,H) $>\mathrm{CH}{}_3>\mathrm{H}$, descriptor S. The compound is (2R,3S)-2-bromo-3-chlorobutane (RDKit labels R and S respectively).