An underground hazardous waste storage tank is leaking. The contaminant concentration directly beneath the site is $0.5 \mathrm{mg} / \mathrm{L}$. The contaminant is travelling at an effective rate of $0.4 \mathrm{~m}$ per day towards a water well which is $2 \mathbf{~ k m}$ away.
Assume that the degradation of the contaminant follows a first order reaction, and the initial concentration of the contaminant becomes half in $10$ years.
In this case, the contaminant concentration expected at the well under steady state conditions is ____________ $\mathrm{mg} / \mathrm{L}$ $\text{(rounded off to two decimal places)}$.
