Back in 1970s, much of the gasoline used in cars contains lead rather than the unlead version found nowadays. A study measured the lead concentration in the air at a highway in Los Angeles USA during weekday afternoons in the Fall of 1976 and 1977. The data is given in lead_concentration.csv. (i) (ii) (iii) [10pt] Load the data into R and make a plot to compare the concentrations in 1976 and 1977 that contains two boxplots, one for the data in each year, arranged side- by-side. (See instructions on R below and check the documentation using help()) [10pt] As a descriptive examination based on the boxplots, which year has a higher lead concentration? What else can you tell from the boxplots? [10pt] Calculate the sample mean and sample standard deviation of the concentration for year 1976 and 1977, after excluding potential outliers (based on the boxplots). Fall 1976 Fall 1977 2.1 3.2 2.9 5 5.7 34 129ain 3.9 4.9 5.2 vi vi 5.4 249 5.9 5 5 10 10 10 10 10 10 10 10 10 10 10 6 6.1 6.1 010 01.0 9 6.2 9 9 6.3 6.4 77 6.4 50 00in AAAAWN 6.4 6.4 6.5 00 00 00 6.7 6.8 00 00 00 00 00 6.9 7.1 7.2 7.6 7.9 7 66 8.1 8.1 113 8.3 8.4 45567 8.5 8.5 8.6 8.7 9 9.2 9.3 9.7 10.9 11.2 10 10 10 10 10 6.3 6.5 un 000 6.6 6.8 7.3 3N 00 00 00 00 00 00 co a ai oi oi ai ai a an ano ano ano OOO 8.1 8.2 N 8.2 32 10 8.3 8.6 8.7 8.9 9.1 9.1 wi 9.3 9.3 9.4 9.4 9.4 9.4 9.5 9.8 9.8 9.9 9.9 10.2 10.3 10.5 10.5 10.7 11.4 12 12.4 14.8 16.7