A homogeneous isotropic confined aquifer of uniform thickness $30 \: \mathrm{m}$ has hydraulic conductivity of $5 \mathrm{~m} / \mathrm{day}$ and porosity of $0.3$. There are two observation wells $\boldsymbol{X}$ and $\boldsymbol{Y}$ along a radial line from a fully penetrating pumping well at $100 \: \mathrm{m}$ and $200 \: \mathrm{m}$ distance, respectively. The well is pumped at a uniform rate to produce steady drawdown of $5 \: \mathrm{m}$ at $\boldsymbol{X}$ and $3 \: \mathrm{m}$ at $\boldsymbol{Y}$. If a non-reactive pollutant enters at the observation well $\boldsymbol{Y}$, then the time taken by the pollutant (under advection) to reach the observation well $\boldsymbol{X}$ is $\_\_\_\_\_\_$ days. (rounded off to two decimal places)
