Two charged dust grains within a planetary ring are separated by a distance of 80 μm80\ \mu\text{m}80 μm. The electrostatic force of repulsion between them is 1.80 μN1.80\ \mu\text{N}1.80 μN. The distance between the dust grains is increased by 160 μm160\ \mu\text{m}160 μm.
What is the new electrostatic force of repulsion?
200 nN200\ \text{nN}200 nN
450 nN450\ \text{nN}450 nN
600 nN600\ \text{nN}600 nN
900 nN900\ \text{nN}900 nN
