The answer is A (Level strategy). I don't understand why it is not time flexibility strategy because overtime was used. Please explain step by step as well as characteristics of level, time flexibility, chase strategies

30. In exercise 9.1a of Chopra & Meindl, the size of the workforce is the most important resource. Suppose that we found the solution to the aggregate planning problem as shown in the table. What type of strategy is followed? A Level strategy Workforce Overtime Inventory Period Demand FIO (hours) (end of periode Production 0 250 5,000 1 10,000 250 0 15,000 20,000 2 11,000 250 01 24,000 20.000 3 15,000 250 0 29,000 20,000 4 18,000 250 ol 31,000 20.000 5 25,000 250 0 0 20,000 6 26.000 250 4,200 22,100 22.100 7 41.000 250 5,000 3,600 22.500 8 26.100 250 5,000 0 22,500 9 18.900 250 0 18,900 10 18,000 250 0 18,000 14.000 250 0 0 14,000 12 11,000 250 ol 5,000 16,000 26,000) B Chase strategy C Time flexibility strategy DHybrid chase and time flexibility strategy E Hybrid chase and level strategy Hybrid chase, time flexibility, and level strategy