3. 200Ci of cesium-137 (Cs-137) are used for the gamma ray source of an experimental food irradiation unit. The half-life of Cs-137 is 11000 days. a. What is the remaining amount of activity of the food irradiation source after 3yr ? [10 points b. Include a plot showing the relationship between remaining Cs-137 activity and time since the setup of the experimental food irradiation unit and indicate half-life in the plot. [15 points]