Flying lessons on weekdays cost m dollars per hour. Flying lessons on weekends cost 1.2m dollars per hour. The expression 9m+3(1.2m) represents the total dollar amount that Maren spent on flying lessons. What does the 9m in the expression represent? A. the cost of all the flying lessons that Maren took on weekends B. the cost of all the flying lessons that Maren took on weekdays C. the number of hours of flying lessons that Maren took on weekdays D. the number of hours of flying lessons that Maren took on weekends