8 Polymer spheres (diameter: 1cm ) made up of a mixture of a rubber and an epoxy resin are being considered as controlled release devices to administer sodium nitrate (an essential nutrient) to underground microorganisms that remediate soils contaminated with hydrocarbons. To load the spheres with sodium nitrate, they are contacted with a solution of sodium nitrate in water. After a long time (at equilibrium), the concentration of sodium nitrate in the spheres reaches a uniform value of 3.02104mol/cm3 while, at the same time, the concentration of sodium nitrate in the liquid is 10104mol/cm3. After loading, the spheres are placed in the soil where they are completely surrounded by flowing water that contains 104mol/cm3 of sodium nitrate. The convective mass transfer coefficient for transfer of sodium nitrate between the flowing liquid and the spheres is 1104cm/s. The diffusivity of sodium nitrate in the polymer material is 1.3105cm2/s. a. Find the time necessary for the spheres to release 80% of the sodium nitrate that they contain when they are initially placed in the soil. b. Calculate the molar flow rate (moles/s) of sodium nitrate from the sphere to the flowing water at the time when 80% of the sodium nitrate has been released