We know that 1 mile is equivalent to 5280 feet. So we have that
[tex]6\frac{ft}{year}=6\frac{ft}{year}\times(\frac{1mile}{5280ft})[/tex]which gives
[tex]\begin{gathered} 6\frac{ft}{year}=6\frac{ft\times1mile}{year\times5280ft} \\ 6\frac{ft}{year}=\frac{6}{5280}\frac{mile}{year} \end{gathered}[/tex]Therefore, we get
[tex]6\frac{ft}{year}=0.0011363\frac{mile}{year}[/tex]By rounding to the nearest thousandth, the answer is:
[tex]0.001\frac{mile}{year}[/tex]