The FD-based solution is performed in the following steps: 1. Discretize the given structure (gridding) using a suitable step size in both dimensions (Ar and Ay). The accuracy of the results improves with smaller step sizes. 2. Approximate the partial derivatives in equation (2) by the following: aV V(i+1, j)-2V(i, j)+V(i-1, j) x (Vx) . (3) 19 aV V(i, j+1)-2V(i, j)+V(i, j-1) dy (Vy) where i and j are the indices along the x-axis and the y-axis respectively. Substituting equations (3) and (4) in equation (2), we get V(i, j)=[V(i+1, j)+V(i-1, j)+V(i, j+1)+V(i, j-1)] ...(5) .(4)