The accompanying data set contains two variables, x$1$ and x$2.$

b$.$ Sort the data by x$1$ and then by x$2,$ both in ascending order. Note that both variables are sorted simultaneously. What are the x$1$ and x$2$ values of the first observation after the data are sorted?

c$.$ Sort the data by x$1$ and then by x$2,$ both in descending order. Note that both variables are sorted simultaneously. What are the x$1$and x$2$ values of the first observation after the data are sorted?

d$.$ Sort the data by x$1$ in ascending order and then by x$2$ in descending order. Note that both variables are sorted simultaneously. What are the x$1$ and x$2$ values of the first observation after the data are sorted?

e$.$ How many missing values are there in x$1$ and x$2?$