The additional output produced from an increase of one unit of labor.
What is the relationship between MP(L) and the total production function?
The marginal product of labor, at any point, is given by the slope (tangent) of the total product function on that same point.
What is the difference between short-run production and long-run production?
In the short run, there is one variable (primarily labor). The other (capital) is fixed.
In the long run, both inputs are variables.
Why would capital be fixed and labor be variable?
It takes time for a firm to adjust its inputs and produce its product with differing amounts of labor and capital. Capital takes time to build or order and deliver. Because of that a firm is unlikely to be able to substitute much capital for labor.
What is the average product of labor?
The output per unit of labor.
How do you calculate the average product of labor?