In the thermite reaction, $\text{Fe}_2\text{O}_3\text{(s)} + 2\text{Al(s)} \rightarrow \text{Al}_2\text{O}_3\text{(s)} + 2\text{Fe(s)}$. Given $\Delta_f H^\ominus$ of $\text{Al}_2\text{O}_3 = -1675.7\ \text{kJ/mol}$ and of $\text{Fe}_2\text{O}_3 = -824.2\ \text{kJ/mol}$, find $\Delta_r H^\ominus$.