1.) Get a big sheet of grid paper. Plot the 28 periods and the resulting number of cases.

2.) Plot each of the defined models on the same sheet for each period.

3.) Determine the difference at each point for each model. Each model will give a better fit for a segment of the actual data. You are not required to design or determine a new model. You are required to analyze the accuracy of the models to the actual data.

That is about what the "Question 3" is requiring you to discuss.