$5\mathrm{.}4-1.$ Consider the model given in Prob. $5\mathrm{.}2-2.$ Let x$6$ and x$7$ be the

slack variables for the first and second constraints, respectively. You

are given the information that x$2$ is the entering basic variable and x$7$

is the leaving basic variable for the first iteration of the simplex

method and then x$4$ is the entering basic variable and x$6$ is the leaving basic variable for the second $($final$)$ iteration. Use the procedure

presented in Sec. $5\mathrm{.}4$ for updating B$1$ from one iteration to the next

to find B$1$ after the first iteration and then after the second iteration.