The capacitance between a pair of identical conducting parallel plates \((A~\&~B),\) placed close together, is \(20\) nF (Fig I). An identical third conducting plate \((C)\) is placed parallel to the other two (Fig. II), so that they form an equidistant system of parallel plates. Plates \(A,C\) are connected by a conducting wire. The capacitance between \(A,B\) is now: