The O'Neill High School Performing Arts Center auditorium contains 20 rows (numbered 1 through 20) with 40 seats each (numbered 1 through 40). Write an application that allows a user to continuously enter a row and seat request until a sentinel value is entered. If the row or seat number is too high, issue an error message. Otherwise, determine whether the seat has already been reserved. If so, display an error message; if not, then charge the user $7.50 for a ticket and display a running total of the user's purchase. When the user enters a sentinel, display the number of seats taken and the number still available in the auditorium.