Suppose we are interested in studying the distribution of the magnitude $`$mag$`$ variable. Write your own R code to make a single figure with the following four subfigures in a $2-$by$-2$ layout.

$-$ subfigure #$1$: plot a density histogram of the earthquake magnitudes, and then plot the estimated probability density curve in red color in the same plot

$-$ subfigure #$2$: plot a horizontal boxplot of the earthquake magnitudes

$-$ subfigure #$3$: plot the empirical cdf of the earthquake magnitudes

$-$ subfigure #$4$: make a Q$-$Q plot to compare the observed earthquake magnitudes distribution with the theoretical Normal distribution. Add a $*$thick$*$ qqline in blue color.