Show that the laminar, free convection correlations for a vertical, isothermal flat plate of height \(L\) can be applied to a vertical, isothermal cylinder of diameter \(D\) and height \(L\) if the boundary layer thickness at the top of the cylinder is approximately one-fourth the cylinder diameter. Determine the critical cylinder diameter, \(D_{\text {crit }}\), below which the flat plate correlations cannot be applied when the surface is at \(T_{s}=35^{\circ} \mathrm{C}\), the surrounding, quiescent air is at \(T_{\infty}=25^{\circ} \mathrm{C}\), and \(L=0.75 \mathrm{~m}\). Calculate the rate of free convection heat transfer from the vertical cylinder wall corresponding to the critical cylinder diameter.