The marginal product can only be identified depending on the status of the total product. In order to find the marginal product, you need to divide the change in the total product, which in this case is significantly lower, by the change in the variable input. It is a relatively easy calculation to do and it goes as follows:

- Firstly, you need to calculate the change that has occurred in the total product. You mentioned that the total product has diminished so let's use an example. If 5 workers have been fired from their posts then it is likely that production will decrease. Let's say it has decreased to 20 units. The 20 units represent the total change.

- Once you have found the total change you should then proceed to calculate the change in the variable input. For example, I stated above that five workers had been fired, and they are the reason why the total product has lowered. Therefore the five workers are the variable input. The change is 5.

- To find the marginal product you need to then divide the change in total product which is 20 by the change in variable product which we calculated as 5. The formula should read as 20/5 = 4. The figure shown in this calculation represents the marginal product.