Deduce the expression for capacitance of parallel plate capacitor with Dielectric slab. between the

Question

$\begin{array}{1 1} (a)\; C= \large\frac{\in_0A}{(d-t)+t/k}\\ (b)\;C= \large\frac{\in_0A}{d+t+k}\\ (c) C= \large\frac{\in_0Ad}{tk} \\ (d) C= \large\frac{Ad}{\in_0tk} \end{array}$