A 22-year-old man is brought to ED 3 hours after ingesting 30 g of paracetamol in a self-harm attempt. He weighs 70 kg and has no significant past medical history. Serum paracetamol level at 4 hours post-ingestion plots above the treatment line on the Rumack-Matthew nomogram. According to updated Australian guidelines, what is the recommended intravenous acetylcysteine regimen?