Berapakah besar gaya coulomb antara kedua muatan tersebut?

diketahui :
Q1 = 2×10⁻⁵ C
Q2 = -3×10⁻⁵ C
k = 9×10⁹
r = 50 cm = 5×10-¹ m

jawab :
F = k Q1 Q2 / r²
F = 9×10⁹ . 2×10⁻⁵ . 3×10⁻⁵ / (5×10-¹)²
F = 54×10-¹ / 25×10-²
F = 2,16×10¹
F = 21,6 N