The Tiernan Gallery and Art Museum distributes to its visitors a printed guide to its collections. There are about 18000 visitors per year. Holding costs for the brochures are 20% and it costs $30 to place an order with the printer. The printer has offered the following discount schedule:
Category Order Size Unit Cost
1 0 - 1499 $2.50
2 1500 - 2999 $2.20
3 3000 and over $1.80
How many brochures should be printed at a time?