Ini gimana? bantu dong kak

F = k × Q1 × Q2/r^2
27.000 = 9 × 10^9 × 3 × 10^-4 × 64 × 10^-4/r^2
27.000 = 1.728 × 10/r^2
r^2 = 1.728 × 10/27.000
r^2 = 1.728/2.700
r^2 = 0,64 m
r = 0.8 m
r = 80 cm