#### Answer

The force is multiplied by 4. The force is multiplied by 16. The force is divided by a factor of 16.

#### Work Step by Step

Coulomb's Law guides our answers, in particular, the inverse-square nature of the law. The force is inversely proportional to the square of the distance.
$$F = k \frac{q_{1} \; q_{2}}{d^{2}}$$
If the two charges are brought closer together, dividing their separation distance by a factor of 2, the force is multiplied by a factor of 4.
If the two charges are brought closer together, dividing their separation distance by a factor of 4, the force is multiplied by a factor of 16.
If the two charges are moved farther apart, multiplying their separation distance by a factor of 4, the force is divided by a factor of 16.