Two identical charges q placed 2.0 m apart exert forces of magnitude 4.0 N on each other. What is the value of the charge q?
a) = 1.8 x 10⁻⁹ C
b) = 2.1 x 10⁻⁵ C
c) = 4.2 x 10⁻⁵ C
d) q = 1.9 x 10⁵ C