1. The spread of the antibiotic cefoperazone through agar gel, fibrin gel, and rat brain tissue was measured by adding a solution of the drug (at a concentration of 5mg/ml ) to the top of each material and then measuring the concentration at different depths at a set time. The experiments with brain tissue were conducted on live rats, while the experiments with agar and fibrin gel were done on Petri dishes (with a thickness of 0.5cm and a diameter of 10cm ). The results are as follows: Create a model of the penetration of cefoperazone into agar, fibrin, or cortex tissue by: 1. Drawing the physical situation 2. Listing at least three assumptions 3. Defining boundary and initial conditions 4. Formulating the proper mathematical equation for mass transfer, using a differential equation