I think one of the most important things to fully understand the shape of the TP (total product) function as we increase use of labor. This tells us how the AP (average product), and MP (marginal product) curves will look like. And, because of the negative relationship between productivity and costs, understanding of the shape of TP, helps us drive the cost functions, such as TC (total cost), AVC (average variable cost), and MC (marginal cost).

Could you briefly explain how and why TP changes between 0 and L1, between L1 and L3, and beyond L3?