A $4 \: m$ wide strip footing is founded at a depth of $1.5 \: m$ below the ground surface in a $c-\phi$ soil as shown in the figure. The water table is at a depth of $5.5 \: m$ below ground surface. The soil properties are: $c’=35 \: kN/m^2, \: \phi‘=28.63^{\circ}, \: \gamma_{\text{sat}} = 19 \: kN/m^3, \: \gamma_{\text{bulk}} = 17 \: kN/m^3$ and $\gamma_u =9.81 \: kN/m^3$. The values of bearing capacity factors for different $\phi ‘$ are given below:

Using Terzaghi’s bearing capacity equation and a factor of safety $F_s=2.5$, the net safe bearing capacity (expressed in $kN/m^2$) for local shear failure of the soil is _______