Which of the following reactions are feasible ? (a) $\text{CH}_3\text{CH}_2\text{Br} + \text{Na}^+ \text{O}^-\text{C}(\text{CH}_3)_3 \rightarrow \text{CH}_3\text{CH}_2-\text{O} - \text{C} (\text{CH}_3)_3$ (b) $(\text{CH}_3)_3 \text{C} - \text{Cl} + \text{Na}^+ \text{O}^- \text{CH}_2\text{CH}_3 \rightarrow \text{CH}_3\text{CH}_2 - \text{O} - \text{C}(\text{CH}_3)_3$ (c) Both (a) and (b) (d) Neither (a) nor (b)