In the simple model of the baryon mass splittings discussed in Section 6.1.4, the electromagnetic interaction

In the simple model of the Σ baryon mass splittings discussed in Section 6.1.4, the electromagnetic interaction energy between two quarks a and b was assumed to be of order δe_ae_b , where e_a and e_b are the quark charges in units of e. Deduce the value of δ obtained from the observed Σ baryon masses in this approximation, and use it to make a rough estimate of the typical distance r between the quarks by assuming that the Coulomb interaction dominates.