In a city with three high schools, all the ninth graders took a Standardized Test, with these results: High School Mean Test Score Number of ninth graders (Frequency) Glenwood 83 263 Central Lincoln 91 67 329 169 The city's PR manager, who never took statistics, claimed the mean score of all ninth graders in the city was the average of 83, 91, and 67, which is 80.3. Of course, that is incorrect. What is the mean score for all ninth graders in the city? Round to one decimal place. Mean of all ninth grader's scores =