A tracer takes $100$ days to travel from Well-$1$ to Well-$2$ which are $100 \: m$ apart. The elevation of water surface in Well-$2$ is $3 \: m$ below that in Well-$1$. Assuming porosity equal to $15 \%$, the coefficient of permeability (expressed in $m/day$) is

1. $0.30$
2. $0.45$
3. $1.00$
4. $5.00$