Consider the following lineer programming problem.

minZ

$=$

$1$

$2$

$$

$1$

$+$

$$

$2$

$2$

$$

$1$

$+$

$$

$2$

$<=$

$1$

$0$

$6$

$$

$1$

$+$

$8$

$$

$2$

$>=$

$4$

$8$

$$

$2$

$<=$

$8$

$$

$1$

$,$

$$

$2$

$>=$

$0$

a

$.$

$$For what values of

$$

$1$

$$does the current basis remain optimal?

b

$.$

$$For what values of

$$

$2$

$$does the current basis remain optimal?