2-19 An assembly line can produce 90 units per hour. The line's hourly cost is $4500 on straight time (the first 8 hours). Workers are guaranteed a minimum of 6 hours. There is a 50% premium for overtime, how- ever. productivity for overtime drops by 5%. What are the average and marginal costs per unit for the following daily quantities?

(a) 450

(b) 600

(c) 720

(d) 900