A $1\mathrm{.}5m$ deep square footing $)=L=1\mathrm{.}0(m),D_f=(1\mathrm{.}5(m)$ carries a downward load of $250kN.$ It is underlain by overconsolidated clay $($OC case $1)$ with the following properties: $C_c=0\mathrm{.}20,C_r=0\mathrm{.}05,e_0=0\mathrm{.}7$ and ${}_n=17\mathrm{.}0k\frac{N}{m^3}($above the groundwater table$)$ and ${}_{\text{s}\text{a}\text{t}}=18\mathrm{.}0k\frac{N}{m^3}($below the groundwater table$).$ The groundwater table is at a depth of $1\mathrm{.}5m$ below the ground surface. The secondary compression settlement is negligible. Determine the coefficient of subgrade reaction.