You use a polymer to surround a foreign cell mass that can secrete insulin and implant the construct in the skin. The goal of polymer encapsulation is to prevent macrophages and other immune cells from attacking the insulin secreting cells (because these cells are foreign the patient's immune cells want to destroy them). The thickness of the polymer layer is 1 mm. Assume diffusivity of insulin through the polymer to be 5x108 cm/s and concentration of insulin inside the construct at 1 mg/cm. The overall diameter of the almost spherical implanted construct is 4 mm. Find the amount of insulin secreted by the implanted construct in ng/s. List your assumptions