In a city with three high schools, all the ninth graders took a Standardized Test, with these results: Number of ninth graders (Frequency) _I_ _-Z-'_ _l_ 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, 94, and 66, which is 81. 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 =