Solution
= Solution
{c}
The unchanged reduced costs remain optimal for a maximization problem. The new basic solution is feasible exactly when $2-\alpha\geq0$ and $14+2\alpha\geq0$. Therefore
$$
\boxed{-7\leq\alpha\leq2.}
$$
The endpoints are included: one basic variable then vanishes, but feasibility and the reduced-cost certificate remain valid.