Managerial Accounting for Managers (4th Edition) Chapter 7, question 31C. The step by step answer to question 2 says there are 450 DLH available in the month. I do not understand how they got 450 DLH's.

2. Refer to the original data. Assume that Zwinger Nursery plans to place regular orders for 20,000-pound lots of the new compound. Wesco expects the demand for GrowNWeed to remain strong. Therefore, the recurring orders from Zwinger would put Wesco over its twoshift capacity. However, production could be scheduled so that 90% of each Zwinger order could be completed during regular hours. As another option, some GrownWeed production could be shifted temporarily to overtime so that the Zwinger orders could be produced on regular time. Current market prices are the best available estimates of future market prices. Wesco's standard markup policy for new products is 40% of the full manufacturing cost, including fixed manufacturing overhead. Calculate the price that Wesco, Inc., would quote Zwinger Nursery for each 20,000 pound lot of the new compound, assuming that it is to be treated as a new product and this pricing policy is followed