When a voltage difference is applied to a piece of copper wire, a 5.0 mA current flows. If the copper wire is replaced with a silver wire with twice the diameter of the copper wire, how much current will flow through the silver wire? The lengths of both wires are the same, and the voltage difference remains unchanged. (The resistivity of copper is 1.68 × 10-8 ?·m, and the resistivity of silver is 1.59 × 10-8 ?·m.)