Cyclopropane, $\mathrm{C}_{3} \mathrm{H}_{6}$, is converted to its isomer propylene, $\mathrm{CH}_{2}=\mathrm{CHCH}_{3}$, when heated. The rate law is first order in cyclopropane, and the rate constant is $6.0 \times 10^{-4} / \mathrm{s}$ at $500^{\circ} \mathrm{C}$. If the initial concentration of cyclopropane is $0.0226 \mathrm{~mol} / \mathrm{L}$, what is the concentration after $899 \mathrm{~s}$ ?