Answer:

Explanation:
According to the Coulomb's law, the magnitude of the electrostatic force between two static point charges
and
, separated by a distance
, is given by

where k is the Coulomb's constant.
Initially,

The negative sign is taken with force F because the force is attractive.
Therefore, the initial electrostatic force between the charges is given by

Now, the objects are then brought into contact, so the net charge is shared equally, and then they are returned to their initial positions.
The force is now repulsive, therefore, 
The new charges on the two objects are

The new force is given by

Using (1),



Using (1),
When
,

When
,

Since, 
Therefore, 