tolong dijawab yg tau

a) F = K × Q1 × Q2/r^2
F = 9 × 10^9 × 4 × 10^-6 × 8 × 10^-6/(4 × 10^-3)^2
F = 288 × 10^-3/16 × 10^-6
F = 18 × 10^3
F = 18.000 C

b) Gaya tarik-menarik