Insects do not have lungs as we do, nor do they breathe through their mouths. Instead, they have a system of tiny tubes, called tracheae, through which oxygen diffuses into their bodies. The tracheae begin at the surface of the insect's body and penetrate into the interior. Suppose that a tracheae is 1.73 mm long with a cross-sectional area of 1.52 x 10-9m2. The concentration of oxygen in the air outside the insect is 0.786 kg/m3, and the diffusion constant is 1.70 x 10-5 m2/s. If the mass per second of oxygen is diffusing through a trachea is 1.96 x 10-12 kg/s, then find the oxygen concentration at the interior end of the tube.