(b) $C = \frac{(C_{1} + C_{2}) \times C_{3}}{\left( C_{1} + C_{2} \right) + C_{3}} = \frac{(5 + 10) \times 4}{5 + 10 + 4} = \frac{60}{19} = 3.2\mu F$
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.