Businessman Elon Musk said people must work up to 100 hours a week to "change the world". Mr Musk started SpaceX, Tesla, and PayPal. His companies have changed our lives. He is a workaholic. He loves working. He said: "There are easier places to work, but nobody ever changed the world on 40 hours a week."

Mr Musk said "everyone" at Tesla has worked 100 hours per week at times this year. Some workers are unhappy with their long hours. Others like to work 70 hours per week. Musk said the "pain level" increases above 80 hours a week. The CEO of a billion-dollar company works about 70 hours a week.