hello i dont understand how to calculate second row

Down Under Products, Ltd., of Australia has budgeted sales of its popular boomerang for the next four months as follows: April May June July Unit Sales 90,000 95,000 130,000 100,000 The company is now in the process of preparing a production budget for the second quarter. Past experience has shown that end-of-month inventory levels must equal 20% of the following month's unit sales. The inventory at the end of March was 18,000 units. Required: Prepare a production budget by month and in total, for the second quarter. June Quarter May 95,000 Down Under Products, Ltd., Production Budget April Budgeted unit sales 90,000 Add: Desired units of ending finished goods inventory 19,000 Total needs 109,000 Less: Units of beginning finished goods inventory 18,000 Required production in units 91,000 115,000 18,000 97,000