Two circular metal plates, $X$ and $Y$, are parallel to each other. Each plate has a diameter of $18\,\text{cm}$, and the gap between the plates is $9.0\,\text{cm}$. A potential difference of $9.0\,\text{V}$ is applied across them. Point $P$ lies $6.0\,\text{cm}$ from the surface of plate $X$ and $3.0\,\text{cm}$ from the surface of plate $Y$. Determine the electric field strength at $P$.
- A$50\,\text{N C}^{-1}$
- B$100\,\text{N C}^{-1}$
- C$150\,\text{N C}^{-1}$
- D$300\,\text{N C}^{-1}$