Transformer voltage regulation: PE Power Electric Power Devices practice question

A 2,500 kVA, 13.8 kV–480Y/277 V substation transformer serving an industrial plant has a nameplate resistance of 1.0% and reactance of 5.5% on its own base. It carries rated load at 0.85 power factor lagging with rated 480 V at the secondary terminals.

The transformer's full-load voltage regulation is most nearly: