The diffusion coefficient of a particular kind of t-RNA molecule is $D=1.0 \times 10^{-11} \mathrm{~m}^2 \mathrm{~s}^{-1}$ in the medium of a cell interior. How long does it take molecules produced in the cell nucleus to reach the walls of the cell at a distance $1.0 \mu \mathrm{m}$, corresponding to the radius of the cell?
1.7