N₂O₅ is Used as a Source of NO₂ in Chemical $\times$

N₂O₅ is used as a source of NO₂ in chemical reactions. The compound decomposes in a first order reaction. If the initial concentration of N₂O₅ = 0.400 M, and the concentration is 0.025 M after 120 seconds, what is the rate constant k of the reaction?

A) 7.50 s^-1
B) 333 s^-1
C) 2.77 s^-1
D) 2.31 $\times$ 10^-2 s^-1
E) 5.21 $\times$ 10^-4 s^-1