In economics, a production function specifies the output that can be produced by various quantities and of inputs, typically labor and physical capital. The production function of a firm or a society can be plotted in three-dimensional space. If a plane section is taken parallel to the -plane, the result is an isoquant showing the various combinations of labor and capital usage that would result in the level of output given by the height of the plane section. Alternatively, if a plane section of the production function is taken at a fixed level of —that is, parallel to the -plane—then the result is a two-dimensional graph showing how much output can be produced at each of various values of usage of one input combined with the fixed value of the other input .