The rate constant $k$, for the reaction $N_2O_{5(g)} \to 2NO_{2(g)} + \frac{1}{2}O_{2(g)}$ is $2.3 \times 10^{-2}$ s$^{-1}$. Which equation given below describes the change of $[N_2O_5]$ with time? ($[N_2O_5]_0$ and $[N_2O_5]_t$ correspond to concentration of $N_2O_5$ initially and at time $t$.)