1 The formula for calculating Marginal Cost (MC) is:

Here are the solutions to your questions:

4.1 The formula for calculating Marginal Cost (MC) is:

$$\text{MC} = \frac{\Delta \text{TC}}{\Delta \text{Q}} \quad \text{or} \quad \text{MC} = \frac{\Delta \text{TVC}}{\Delta \text{Q}}$$

Where $\Delta \text{TC}$ is the change in Total Cost, $\Delta \text{TVC}$ is the change in Total Variable Cost, and $\Delta \text{Q}$ is the change in Quantity.

4.2 The formula for calculating Average Cost (AC) is:

$$\text{AC} = \frac{\text{TC}}{\text{Q}}$$

Where $\text{TC}$ is Total Cost and $\text{Q}$ is Quantity.

4.3 Marginal cost is the additional cost incurred by producing one more unit of a good or service. It represents the change in total cost when output increases by one unit.

4.4 Calculate the value of TC labelled A.