please explain how you get total inventory cost

Consuelo Chua, Inc., is a disk drive manufacturer in need of an aggregate plan for July through December. The company has gathered the following data. There are 8 hours of production per day. Holding oost Subcontracting Regular-time labor Overtime labor Hiring cost Layoff cost Costs SB/disk drive/Month $80/disk drive $12/hour $18/hour (above 8 hours) S40/worker S80/worker Other Data Current workforce (June) 8 people Labor-hours/disk drive 4 hours Workdays/month 20 days Beginning Inventory 150 disk drives Ending Inventory O disk drives "Note that there is no holding cost for June. What will the following strategy cost? This exercise only contains part a a) Vary the workforce so that production approximates demand. Chua had eight workers on board in June. Enter al responses as whole numbers). Fill in the table below. (Enter all responses as whole numbers in the hire/layoff column, use positive numbers for hires-plus signs omitted, negative numbers for layoffs.) Units Produced Hire / Layoff Demand Plan A Beginning Personnel on Inventory Staff 150 150 - 10 13 240 Month 0 June 1 July 2 August 3 September 4 October 5 November 8 December 400 500 550 700 800 700 14 SSN No costs are incurred for unmet demand, "When computing "Personnel on Staff" 0.5 or more of an employee is needed round up and hire one more employee; if less than 0.5, round down. The total inventory cost = $ 400 (Enter your response as a whole number) The total hiring cost = $ 560. (Enter your response as a whole number) The total layoff cost = $ 320. Enter your response as a whole number) The total cost excluding normal time labor costs, is = $ 1.280. (Enter your response as a whole number)