A dielectric is completely filled between the space of a parallel plate capacitor. The separation between plates of capacitor is ‘$d$’ and dielectric constant is given by $k=k_0{e}^{\lambda x}$ where '$k_0$' and '$\lambda$' are positive constants and $x$ is distance from one plate of capacitor. If distance between plate (d) increases slowly then graph between capacitance of capacitor and distance between plate is given by