For a solid embryo in contact with a perfectly flat mould wall as shown in the schematic, the wetting angle θ is _______ degrees. (Round off to one decimal place). Given: Surface tension between liquid and mould wall = 0.35 J⋅m^-2 Surface tension between solid and mould wall = 0.02 J⋅m^-2 Surface tension between liquid and solid = 0.40 J⋅m^-2