4. In her 2011 book, author and video game designer Jane McGonigal reports that "The average young person racks up 10,000 hours of (video) gaming by the age of 21. That's almost exactly as much time as they spend in a classroom during all of middle school and high school if they have perfect attendance" (Source: Reality is Broken: Why Games Make Us Better and How They Can Change the World). If the daily average time that 18-year-olds spend playing video games has a normal distribution with a mean of 2.5 hours and a standard deviation of .7 hours, what percentage of 18-year-olds play games a) at least 4 hours a day? b) no more than 1 hour a day? c) how many hours must an 18-year-old play video games in order to be among the top 1% of game players (measured by time played, not success)