In an aorta that has a radius of \(11 \mathrm{~mm}\) and a transmural pressure (pressure difference across the aorta wall) of \(12 \mathrm{kPa}\), blood is moving in laminar flow at \(350 \mathrm{~mm} / \mathrm{s}\). What percentage of the cross-sectional area of this aorta must be blocked in order for the transmural pressure in the blocked part to fall to zero? Assume that the blood has a mass density of \(1060 \mathrm{~kg} / \mathrm{m}^{3}\) and is nonviscous, incompressible, and undergoing laminar flow at a speed of \(350 \mathrm{~mm} / \mathrm{s}\) in the unobstructed part. Ignore any pressure variation with height.