Identify whether each scenario is an example of marginal cost, a marginal benefit, or neither. All scenarios should be classified into a category.
a. Scenario 1: Purchasing an additional unit of a product increases total revenue.
b. Scenario 2: Increasing production by one unit leads to a decrease in profit.
c. Scenario 3: Hiring one more employee results in a slight decrease in productivity.
d. Scenario 4: Adding another ingredient to a recipe improves the taste slightly.