Tesla shares spiked 11.2% on Monday, boosting Elon Musk’s net worth by $7 billion to $83.6 billion. The hefty stock gain makes the 49-year-old entrepreneur the fifth-richest person in the world, pushing Musk ahead of Indian oil and gas tycoon Mukesh Ambani and investing luminary Warren Buffett. Not that he’s keeping track. The eccentric billionaire […]