Consider the reaction below. Over the course of 123 seconds, the concentration of NO2 decreased by 1.37 x 10-2 M.

O₂(g) + 4 NO₂(g) = 2 N₂O₅(g)

a. Calculate the normalized average reaction rate over this time period.

b. Over the same period of time, if the initial concentration of N2O5 was 2.94 x 10-2 M, calculate the final concentration of N2O5.

No order of reaction is provided for this problem. Based on the given information, answer A and B.