Fault current SLG: PE Power Transmission and Distribution practice question

A 12 MVA, 69 kV Δ / 12.47 kV grounded-wye substation transformer has an impedance of 7.5% on its own rating; take its positive-, negative- and zero-sequence impedances as equal. The 69 kV system at the transformer high side has a three-phase short-circuit level of 1,200 MVA and a single-line-to-ground short-circuit level of 1,000 MVA. The transformer neutral is solidly grounded. Neglecting resistance and pre-fault load, the current in a bolted single-line-to-ground fault at the 12.47 kV transformer terminals is most nearly: