Georges asked five of his friends how long they studied for the last math test and what grade they received. he found a linear regression equation for the data to be y = 9.6x + 65.8. what does the 9.6 mean in the context of this equation? a) his friends on average studied 9.6 hours. b) if they studied 9.6 hours they would get a 0 on the test. c) they should study 9.6 hours in order to get an a on the test. d) for every hour they studied their grade would go up 9.6 points.