An infinite slope is made up of cohesionless soil with seepage parallel to and up to the sloping surface. The angle of slope is 30^o with respect to horizontal ground surface. The unit weights of the saturated soil and water are 20 kN/m³ and 10 kN/m³, respectively.
The minimum angle of shearing resistance of the soil (in degrees) for the critically stable condition of the slope is _______. (rounded off to the nearest integer).