Consider a lamellar eutectic microstructure where the -phase is the minority phase. If the center-tocenter separation between sheets of the -phase phase is fixed at , the total surface area between and remains fixed, even as the amount of decreases and its lamellae are thinner. It may become favorable for the -phase to form as rods when its fraction of the volume is small (see transition in schematic diagram below). Assuming that the rods grow in the arrangement of a square of edge length , what is the critical volume fraction of in for the transition from lamellae to rods be favored