Calculate the optical efficiency on November 13 of an evacuated tube collector array at noon and \(2 \mathrm{p} . \mathrm{m}\). if the direct normal insolation is \(600 \mathrm{~W} / \mathrm{m}^{2}\) and the diffuse insolation is \(100 \mathrm{~W} / \mathrm{m}^{2}\). The effective optical transfer function \(\tau_{e} \alpha_{r}\) is \(70 \mathrm{j}\) percent, and the tubes are spaced one diameter apart in front of a white painted surface with a reflectance \(ho\) of \(60 \%\).