Which one is correct?

In Aggregate Planning a firm practices a chase strategy. Production last quarter was 1200 . Demand over the next four quarters is estimated to be 900,700,1000, and 1000 . Hiring cost is $20 per unit, and layoff cost is $5 per unit. Over the next year, what will be the sum of hiring and layoff costs? $500 $7,500 $2,500 8,500 $12,500