A 0.03-in-thick copper plate (k=223 Btu / h \cdot ft \cdot{ }^{\circ} F) is sandwiched between two 0.1-in.-thick epoxy boards (k = 0.15 Btu / h \cdot ft \cdot{ }^{\circ} F) that are 7 \text { in. } \times 9 \text { in. } in size. Determine the effective thermal conductivity of the board along its 9-in.-long side. What fraction of the heat conducted along that side is conducted through copper?