A Possible Reaction of Ethane with Chlorine Is Shown Below

A possible reaction of ethane with chlorine is shown below.


This reaction could conceivably occur by the following chain mechanisms [1], [2], and [3]. Determine DH for step [2].
Bond dissociation energies (kcal/mol) :

$\begin{array}{|ll|}\hline \text { Bond } \mathrm{A}-\mathrm{B} & \Delta \mathrm{H} \\\hline \mathrm{Cl}-\mathrm{Cl} & 58 \\\mathrm{CH}_{3}-\mathrm{H} & 104 \\\mathrm{CH}_{3} \mathrm{CH}_{2}-\mathrm{H} & 98 \\\mathrm{CH}_{3} \mathrm{CH}_{3} & 88 \\\mathrm{CH}_{3} \mathrm{CH}_{2}-\mathrm{Cl} & 81 \\\mathrm{H}-\mathrm{Cl} & 103 \\\hline\end{array}$

A) +58 kcal/mol
B) -5 kcal/mol
C) None of the choices are correct.
D) -28 kcal/mol