A manufacturer of heavy truck engines must develop an aggregate production plan, given the forecasts for engine demand shown below. The company currently has 13 workers and makes 130 engines per month. Regular labour cost is $500 per engine. The beginning inventory is zero. Overtime labour costs $750 per engine. Hiring cost is $2,000 per worker and layoff cost is $1,000 per worker. Inventory holding cost is $50 per engine per month, and backorder cost is $250 per engine per month. Develop tire minimum cost aggregate production plan for this company.