For the US_contagious_disease dataset, solve:

#Find the top 5 states with the most "Mumps" cases over the 10 years from 1991 to 2000.

# For the state of Texas:
(a) Add variable ave_count, representing the average reported case count per weeks_reporting for each year,
(b) Plot ave_count against the year while using different colors for different disease.
(c) Remove all the observations for disease "Measles" and redo the plot in (b)

#For each state and year, find
(a) The total count for all disease for the given state and year
(b) The diease count density, which is defined by the total count of all disease divided by the population for the given state and year.

#Using the results in Q3, find
(a) The 5 state and year pairs that have the largest total count of all disease
(b) The 5 state and year pairs that have the largest disease count density