Two reservoirs having a difference of $20 \mathrm{~m}$ in their water surface elevations are connected through a confined aquifer (thickness $=5 \mathrm{~m}$, length $=2 \mathrm{~km}$, hydraulic conductivity $K=3 \times 10^{-3} \mathrm{~m} / \mathrm{s}$, and porosity $\eta=0.3$ ) as shown in the following figure (drawn not to scale).
If the Reservoir 1 is contaminated by a pollutant then the time (in days, rounded off to one decimal place) taken by the pollutant to reach to the Reservoir 2 under advection will be
