Cubic shape gel beads of 8 mm on a side contains residual solvent from the gel-casting process. Initially the bead contains 0.20 % of residual solvent uniformly distributed within the polymer. The residual solvent will be removed from the bead by drying the beads in a fluidized bed of fresh air. The air flow though the fluidized bed is very high so that convective mass transfer resistance is negligible (i. e. Kc is extremely high). a. What is the residual concentration at the surface of the bead after 50 hrs? Use, DAB = 4X10-7 cm2 /s. b. If this geometry is approximated as a semi-infinite medium, how long it will take for the solvent to reach 0.18% composition at a depth of 0.1 mm from the surface of the bead. Please solve taking the system as a semi-infinite medium