The Mayor of City A claims that his campaign on "Do NOT eat too many salt" has been a great success. He claims that in the year 2020, the city citizens averagely eat 4500mg salt per day, while the standard error is 300mg. Note: Just use Z score and Z-table if needed.

a. WHO recommends 5000mg salt per day. Can the Mayor claim that his city eats less salt per day than the WHO recommendation level, using 95% confidence interval? Explain how you can get your conclusion in detail (10 points)

b. What are the 95% confidence interval of the Salt eating for the City A citizens? (10 points)