We can reveal the influence of including extra of a variable useful resource, say labor, to a set number of funds and see what happens to output. For demonstration needs in economics, we often make widgets, which is https://www.youtube.com/watch?v=-nQTR6bXhfU&list=PLZ3DkIWtVYetfvXsAvY04--yisQJg2WWI&index=9&pp=iAQB