The following graph shows equilibrium in a free market, with equilibrium quantity of QE . A graph plots equilibrium in a market, with price on the vertical axis and quantity on the horizontal axis. An upward sloping straight-line supply curve intersects a downward-sloping straight-line demand curve at equilibrium quantity of Q sub E. The point of intersection is denoted by a black plus symbol, and dashed black lines extend vertically to the x-axis and horizontally to the y-axis. PRICE QUANTITY Demand Supply Q E For any level of output equal to QE , a buyer values a unit of goods in this market the unit will cost a seller. Suppose now that a firm that produces for this market is able to emit particulate matter into the air surrounding its production facility, harming wildlife and negatively affecting the breathing of nearby residents. This is an example of due to