Using the bond dissociation energies $\mathrm{H}-\mathrm{Cl}=431$, $\mathrm{H}-\mathrm{Br}=366$ and secondary C-H $=410\mathrm{kJ}\mathrm{mo}{\mathrm{l}}^{-1}$, the enthalpy changes (kJ/mol) of the step $\mathrm{R}\cdot +\mathrm{HX}\to \mathrm{R}-\mathrm{H}+\mathrm{X}\cdot$ (R = secondary alkyl) for X = Cl and X = Br respectively are

1. A+21 and -44
2. B-21 and -44
3. C-21 and +44
4. D+21 and +44