DID I GET THIS CORRECT?

Following are the demand, total revenue, marginal revenue, total cost and marginal cost schedules {All in $1 for a monopolist publisher of a textbook in Microeconomics. N umber of Price Total Total Cost Marginal Marginal books per Revenue Revenue Cost hour 0 8 'l2 1 T l 5 2 i5 1 7' 3 5 20 4 4 24 5 3 29 When the monopolist publisher maximizes its profits, what would be his total cost [$] per hour? ANSWEFI 20