A circuit contains two ideal batteries with emfs \(\varepsilon_1\) and \(\varepsilon_2\), and three resistors with resistances \(R_1\), \(R_2\), and \(R_3\), arranged in a two-mesh network as shown. Both batteries are oriented with their positive terminals connected toward the upper conductor. In terms of the given quantities, which of the following expressions is equal to the magnitude of the downward current \(I_2\) through resistor \(R_2\)?