The demand for a commodity generally decreases as the price is raised. Suppose that the demand for oil (per capita per year) is [math] barrels, where [math] is the price per barrel in dollars. Find the demand when [math]. Estimate the decrease in demand if [math] rises to [math] and the increase in demand if [math] is decreased to [math].

The demand [math] = .

The decrease in demand = barrels.

The increase in demand = barrels.