The force between a pair of charges is 100 Newtons. The distance between the charges is 0.01 m. If one of the charges is 2 × 10¹⁰ C, the other charge is ______.
a) 1 × 10⁹ C
b) 4 × 10⁹ C
c) 5 × 10⁹ C
d) 8 × 10⁹ C