The dimensions of a conductance cell are 0.15dm & 0.95dm and the electrodes are separated by 0.05dm. What is cell constant for this cell?

Question

$\begin{array}{1 1}(A)\;1/3.45dm^{-1}&(B)\;1/2.85dm^{-1}\\(C)\;1/9.35dm^{-1}&(D)\;1/4.35dm^{-1}\end{array}$