15. A wooden rod of uniform cross section and of length l is hinged at the bottom of a tank which is filled with water to a height h = l/3, as shown in right figure. If the density of wood is 0.45 g/cm³, find the angle θ from the vertical at which the rod is in equilibrium. (A) θ = 60° (B) θ = 30° (C) θ = 45° (D) θ = 37° (E) θ = 53°