This partial production function shows how output increases as
more capital is being employed while workhours remain fixed. Its
graph is obtained by placing a vertical cut through the 3D production
function parallel to the axis measuring the capital stock.
The slope of the partial production function measures how much output
is gained by a given small increase of the capital stock. This slope
is called the marginal product of capital. The two tangency lines
measure this marginal product of capital at K_{1} and K_{2}.
They indicate that the marginal product of capital becomes smaller
and smaller as the capital stock rises.
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