Figure shows two conducting thin concentric shells of radii r and 3r . The outer shell carries charge q . Inner shell is neutral . Find the charge that will flow from inner shell to outer after the switch S is closed .

Question

$(a)\;\large\frac{q}{3}\qquad(b)\;-\large\frac{q}{3}\qquad(c)\;zero\qquad(d)\;\large\frac{q}{2}$