A Simplex Tableau Is Shown Below ADo One More Iteration of the Simplex Procedure

A simplex tableau is shown below. $$\begin{array} { c c | c c c c c c | c } & & \mathrm { x } _ { 1 } & \mathrm { x } _ { 2 } & \mathrm { x } _ { 3 } & \mathrm {~s} _ { 1 } & \mathrm {~s} _ { 2 } & \mathrm {~s} _ { 3 } & \\\text { Basis } & \mathrm { c } _ { \mathrm { B } } & 3 & 5 & 8 & 0 & 0 & 0 & \\\hline \mathrm { s } _ { 1 } & 0 & 3 & 6 & 0 & 1 & 0 & - 9 & 126 \\\mathrm {~s} _ { 2 } & 0 & - 5 / 2 & - 1 / 2 & 0 & 0 & 1 & - 9 / 2 & 45 \\\mathrm { x } _ { 3 } & 8 & 1 / 2 & 1 / 2 & 1 & 0 & 0 & 1 / 2 & 18 \\\hline & \mathrm { z } _ { \mathrm { j } } & 4 & 4 & 8 & 0 & 0 & 4 & 144 \\& \mathrm { c } _ { \mathrm { j } } - \mathrm { z } _ { \mathrm { j } } & - 1 & 1 & 0 & 0 & 0 & - 4 &\end{array}$$
a.Do one more iteration of the simplex procedure.
b.What is the current complete solution?
c.Is this solution optimal? Why or why not?