Elon Musk says Tesla can fix South Australia’s blackouts in 100 days, or battery system is free

Tesla Inc. Chief Executive Elon Musk is betting that his company can get a battery system in South Australia installed and working within 100 days — and if it can’t, he says, the company will do it free. Musk made the wager Thursday night in a brief back-and-forth on Twitter with Australian software billionaire Mike Cannon-Brookes.…