FILE$\_$Exercise$\_2\mathrm{.}8.$ The accompanying data file contains two numerical variables, $x_1$ and $x_2.$

a$.$ For $x_2,$ how many of the observations are equal to $2?$

b$.$ Sort $x_1$ and then $x_2,$ both in ascending order. After the variables have been sorted, what is the first observation for $x_1$ and $x_2?$

c$.$ Sort $x_1$ and then $x_2,$ both in descending order. After the variables have been sorted, what is the first observation for $x_1$ and $x_2?$

d$.$ Sort $x_1$ in ascending order and $x_2$ in descending order. After the variables have been sorted, what is the first observation for $x_1$ and $x_2?$

e$.$ How many missing values are there in $x_1$ and $x_2?$