Answer:F = -2.4 * 10¹⁰ N
Step-by-step explanation:To get the electric force between two charges, we would use Coulomb's law which states that:
F =

where:
F is the force between the two charges
k is Coulomb's constant = 9 * 10⁹ Nm²/C²
q1 is the first charge = 0.0072 C
q2 is the second charge = -0.006 C
d is the distance between the two charges = 0.004 m
Substitute with the givens in the above formula to get the force between the two charges as follows:
F =

F = -2.4 * 10¹⁰ N
Hope this helps :)