(d) $C = \frac{\varepsilon_{0}A}{\frac{d_{1}}{K_{1}} + \frac{d_{2}}{K_{2}}}$ $= \ \frac{\varepsilon_{0}A}{\frac{d}{2}\left( \frac{1}{1} + \frac{1}{2} \right)} = \frac{4\varepsilon_{0}A}{3d}$
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.