1 mole of oxygen is heated at constant pressure (1 atm) from $ 20^\circ C $ to $ 80^\circ C $, and then cooled from $ 80^\circ C $ to $ 20^\circ C $ at constant volume. If $ C_p = 7.03 \, \text{cal/mol}^\circ\text{C} $ and $ C_v = 5.04 \, \text{cal/mol}^\circ\text{C} $, what is the difference between the heat supplied and the heat rejected?