Keeping $c_1$ constant at $c_1=5,$ the interval for the net change in $c_2,$ represented by $c_2,$ while the current optimal solution remains optimal is

$\frac{2}{3}-c_2\frac{11}{6}$

$-\frac{2}{3}{c}_2-\frac{11}{6}$

$-\frac{10}{3}{c}_2\frac{11}{6}$

$-\frac{2}{3}{c}_2\frac{11}{6}$

none of the above