A neutron consists of one "up" quark of charge $+2 e / 3$ and two "down" quarks each having charge $-e / 3$. If we assume that the down quarks are $2.6 \times 10^{-15} \mathrm{~m}$ apart inside the neutron, what is the magnitude of the electrostatic force between them?

$3.8 N$