Refer to the graph showing a person's immune response, first to a vaccination, and later to exposure to the pathogen that the vaccine targeted.Time is represented on the x-axis, but the scale is different for each subdivision. 
What amount of time does each period typically represent?
Definitions:
Marginal Benefits
The improvement in benefit or utility realized by consuming or producing one more unit of a good or service.
Least-Cost Production
An economic principle where firms seek to produce their output at the minimum possible cost to maximize efficiency and profitability.
Inward Shift
A movement towards the origin of a supply or demand curve, indicating a decrease in supply or demand for a product.
Production Possibilities Curve
A graph representing the maximum combination of goods and services that can be produced with available resources and technology.
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