Use the collision theory of gas-phase reactions to calculate the theoretical value of the second-order rate constant for the reaction D2 (g) + Br2 (g) →2 DBr (g) at 450 K, assuming that it is elementary bimolecular. Take the collision cross-section as 0.30 nm, the reduced mass as 3.930 u, and the activation energy as 200 kJ mol-1