Calculate Y in the lungs when p50 = 25 torr, n = 2.9, and pO₂ = 98 torr. Then, calculate Y in the capillaries, where pO₂ = 23 torr (and p50 and n remain the same). What is the overall efficiency (expressed as a percent to the nearest ones) between the fractional saturation in the lungs minus the fractional saturation in the tissues?