4. Formulating the proper mathematical equation for mass transfer, using a differential equation. The solution for the release can be given by: CsC=raerfc[2Dtra] where a is the radius of the catheter, r is the distance from the center of the catheter, and C/Cs is the concentration in the tissue relative to the concentration at the tip. At a time point of 6h (and given information in the table), plot the above equation and determine the diffusion coefficient for dexamethasone