I have already tried putting the beginning inventory as 640, it said it was wrong.

Johnson Manufacturing produces self-watering planters for use in upscale retail establishments. Sales projections for the first five months of the upcoming year show the estimated unit sales of the planters each month to be as follows: (Click the icon to view additional information.) Inventory at the start of the year was 640 planters. The desired inventory of planters at the end of each month should be equal to 20% of the following month's budgeted sales. Each planter requires four pounds of polypropylene (a type of plastic). The company wants to have 10% of the polypropylene required for next month's production on hand at the end of each month. The polypropylene costs $0.25 per pound. Read the requirements. i Data Table -X Number of planters to be sold January ..... 3,200 Johnson Manufacturing Direct Materials Budget For the Months of January through March January February March Quarter Units to be produced 3,280 3,500 3,380 10,160 Multiply by: Quantity of direct materials needed per unit Quantity needed for production 13,120 14,000 13,520 40,640 Plus: Desired ending inventory of direct materials | 1,400 1,352 1,816 1,816 Total quantity needed 14,520 15,352 15,336 42,456 Less: Beginning inventory of direct materials I . 1,400 1,352 Quantity to purchase 13,952 13,984 Multiply by: Cost per pound $ 0.25 S 0.25 S 0.25 $ 0.25 Total cost of direct material purchases $ 3,488 S 3,496 February March........ April.. 3,600 3,100 4,500 4,700 May... Print Done Enter any number in the edit fields and then click Check