Task: Text Categorization
Input (English): A function that gives this quantity at a fixed level of utility is a "compensated" function. Changes in the curve that represents this quantity can be the result of the substitution and income effects. The Slutsky equation relates the Hicksian and Marshallian functions of this quantity. Giffen goods do not conform to the namesake law of this quantity. This quantity has a downward-sloping curve, and is defined as the willingness and ability to purchase a commodity or service. For 10 points, name this economic quantity, often paired with supply.
Output (English): Social Science