Please I need help with this exercise

Exercise 9-54 Direct Materials Purchases Budget Langer Company produces plastic items, including plastic housings for humidifiers. Each hous- ing requires about 15 ounces of plastic costing $0.08 per ounce. Langer molds the plastic into the proper shape. Langer has budgeted production of the housings for the next 4 months as follows: Units July 3,500 August 4,400 September 4,900 October 6,300 Inventory policy requires that sufficient plastic be in ending monthly inventory to satisfy 20% of the following month's production needs. The inventory of plastic at the beginning of July equals exactly the amount needed to satisfy the inventory policy. Required: Prepare a direct materials purchases budget for July, August, and September, showing purchases n units and in dollars for each month and in total