Let DEF be a rectangular triangle such that D=[0 0 0], E=[3 0 0] and F=[0 4 0]. On the sides DE, DF and EF are constructed respective half-circles with positive z-axis and perpendicular to the xy-plane. Determine the parameters A, B, C of the plane A*x + B*y + C*z = 1 , that tangents the three half-circles.