A capacitor of capacitance $\mathbf{C}$ having vacuum if dielectric of width $\mathbf{d/3}$ is inserted in between of dielectric constant k.
Find new capacitance of capacitor
(A) $\frac{3\mathrm{kC}}{\mathrm{k} + 1}$
(B) $\frac{\mathrm{kC}}{2\mathrm{k} + 1}$
(C) $\frac{3\mathrm{kC}}{2k}$
(D) $\frac{3\mathrm{kC}}{2\mathrm{k} + 1}$