D3.2. Calculate D in rectangular coordinates at point P(2, -3, 6) produced by: (a) a point charge QA = 55 mC at Q(-2, 3, -6); (b) a uniform line charge PLB 20 mC/m on the x axis; (c) a uniform surface charge density Psc = 120 μC/m² on the plane z = -5 m. Ans. 6.38ax - 9.57ay + 19.14az µC/m²; -212a, + 424az μC/m²; 60az μC/m²