A granular soil has a saturated unit weight of 20 kN/m³ and an effective angle of shearing resistance of 30°. The unit weight of water is 9.81 kN/m³. A slope is to be made on this soil deposit in which the seepage occurs parallel to the slope up to the free surface. Under this seepage condition for a factor of safety of 1.5, the safe slope angle (in degree, round off to 1 decimal place) would be _______.