Atube has a length of 0.035 m and a cross-sectional area of 7.3 x 10-4 m2. the tube is filled with a solution of sucrose in water. the diffusion constant of sucrose in water is 5.0 x 10-10 m2/s. a difference in concentration of 5.1 x 10-3 kg/m3 is maintained between the ends of the tube. how much time is required for 3.1 x 10-13 kg of sucrose to be transported through the tube?