Correct answer is 395 please explain how we can get that answer

Question 13 D 'l 1 \"ts NowJuice, Inc. produces bottled pickle juice. A planner has developed an aggregate forecast for demand (in cases) for the next four months. Use the following information to develop an aggregate plan using the LEVEL strategy. Inventory holding cost is $1 per month per case and backlog cost is $5 per month per case. Beginning inventory is zero. Month May June July August Forecast 652 469 3'59 5373 Cost Per Unit Monthly Capacity Regular Production 15.67 400 Overtime Production 1.5 x Regular Prod Cost 400 What is the cost of backlogs over the planning horizon using the LEVEL plan ? I' i 395 margin of error +-0.001