c
Work done \(\mathrm{AB}=\frac{1}{2}(8000+6000)\) Dyne \(/ \mathrm{cm}^2 \times\) \(4 \mathrm{~m}^3=\left(6000 \mathrm{Dyne} / \mathrm{cm}^2\right) \times 4 \mathrm{~m}^3\)

Work done \(\mathrm{BC}=-\left(4000\right.\) Dyne \(\left./ \mathrm{cm}^2\right) \times 4 \mathrm{~m}^3\)

Total work done \(=2000\) Dyne \(/ \mathrm{cm}^2 \times 4 \mathrm{~m}^3\)

\(=2 \times 10^3 \)  \(\times \frac{1}{10^5} \frac{\mathrm{N}}{\mathrm{cm}^2} \times 4 \mathrm{~m}^3 \)

\( =2 \times 10^{-2} \times \frac{\mathrm{N}}{10^{-4} \mathrm{~m}^2} \times 4 \mathrm{~m}^3 \)

\( =2 \times 10^2 \times 4 \mathrm{Nm}=800 \mathrm{~J}\)