b
Let \(\mathrm{I}_{1}\) be the current throug \(5 \,\Omega\) resistance, \(\mathrm{I}_{2}\) through \((6+9) \,\Omega\) resistance. Then as per question,

\(\mathrm{I}_{1}^{2} \times 5=20\) or, \(\mathrm{I}_{1}=2\, \mathrm{A}\)

Potential difference across \(C\) and \(D=2 \times 5\) \(=10 \,\mathrm{V}\)

Current \(I_{2}=\frac{10}{6+9}=\frac{2}{3}\, A\)

Heat produced per second in \(2\,\Omega\)

\(=\mathrm{I}^{2} \mathrm{R}\left(\frac{8}{3}\right)^{2} \times 2=14.2\,\mathrm{cal} / \mathrm{s}\)