Use R to solve.

20 northern red oak seedlings exposed to a fungus were grown in a greenhouse. All seedlings were planted in the same type of soil and received the same amount of sunshine and water. Half received no nitrogen at planting time, to served as a control, and the other half received 368 ppm of nitrogen in the form NaNO₃ The stem weights, in grams, at the end of 140 days were recorded and were saved in variables x1 (control) and x2 (nitrogen), by the R code given below:

x1=c(0.42, 0.24, 0.41, 0.34, 0.23, 0.28, 0.37, 0.42, 0.33, 0.38)

x2=c(0.55, 0.80, 0.61, 0.58, 0.48, 0.53, 0.67, 0.71, 0.49, 0.59)

a) Produce overlayed quantile-quantile plots for the two groups of stem weights and produce comparative boxplots for the two groups of stem weights. Is it reasonable to assume that the stem weights are normally distributed? Is it reasonable to assume that the variances of the stem weights are the same for the groups?