A furniture manufacturer is considering the purchase of a special machine costing $20,000. It can be used to make tables, chairs, and ladders. The variable costs for those are $20, 10, and 15; their selling prices are $50, 20, and 40 respectively. Number of chairs sold would be at least 6 times the number of tables, but no more than 8 times; number of ladders sold would be no more than the number of tables sold. At what revenue will they break even?