When patients are given certain antibiotics, they sometimes get an inflammation of the colon that is usually caused by a bacterium, Clostridium difficile, which produces an endotoxin. The mechanism by which this endotoxin causes damage to the cells lining the colon is not clear. Therefore, Hecht and colleagues* studied the effect of this endotoxin on the permeability of cultured intestinal cells. They measured permeability by two methods, the flux of mannitol across the layer of cells and the resistance of the layer of cells (the data are in Table D-44, Appendix D). A. Quantify the relationship between mannitol flux F and epithelial cell resistance R using a sum of exponentials. B. If a sum of exponentials proves unsatisfactory, propose an alternative model.