Write a linear cost function for the situation. Identify all variables used. A parking garage charges 9 dollars plus 75 cents per half-hour. Identify all variables used. Choose the correct answer below. O A. C(x) represents the cost for parking x cars in the parking garage B. C(x) represents the cost for using the parking garage for x half-hours. C. C(x) represents the number of hours the parking garage was used after paying x dollars. OD. C(x) represents the number of half-hours the parking garage was used after paying x dollars. A linear cost function for the situation is C(x) = (Use integers or decimals for any numbers in the expression.)