According to the quark model of fundamental particles, neutrons-the neutral particles in an atom's nucleus-are composed of three quarks. Two of these quarks are "down" quarks, each with a charge of -e>3; the third quark is an "up" quark, with a charge of +2e>3. This gives the neutron a net charge of zero. What is the electric potential energy of these three quarks, assuming they are equidistant from one another, with a separation distance of 1.3 × 10-15 m? (Quarks are discussed in Chapter 32.)