In a numerical table with 10 rows and 10 columns, each entry is either a 9 or a 10. If the number of 9s in the ~$n$~ throw is ~$n$~-1 for each n from 1 to 10, what is the average(arithmetic mean) of all the numbers in the table?

9.45

9.50

9.55

9.65

9.70