A total of 5 CVD patients were followed up for death. The data is shown in the graph below. (note: If it does reach at the end of year, the blue bar locates in the middle of the year) Participants 1 2 3 4 5 Year 0 Year 01 Year 02 Year 0 Follow up years 2a. How many person years does the cohort contribute to at the end of year 3 ? 2b. What is the case fatality rate for the first two years in this cohort?.