The gas phase decomposition of dimethyl ether at $500C$

$C{H}_{3}OC{H}_3(g)C{H}_4(g)+H_2(g)+CO(g)$

is first order in $C{H}_{3}OC{H}_3$ with a rate constant of $4\mathrm{.}00{10}^{-4}{s}^{-1}.$

If the initial concentration of $C{H}_{3}OC{H}_3$ is $0\mathrm{.}136M,$ the concentration of $C{H}_{3}OC{H}_3$ will be M after $3018$ s have passed.