puts are variable. 5. Fixed cost plus variable cost.: i Fixed cost plus variable cost. 6. The additional revenue a firm receives from selling another unit of output.: c The additional revenue a firm receives from selling another unit of output. 7. The cost of inputs that do not vary with the amount of output produced.: a The cost of inputs that do not vary with the amount of output produced. 8. The amount of output that gives a firm as much profit as possible.: The amount of output that gives a firm as much profit as possible. 9. Selecting inputs in order to produce a desired level of output at the lowest cost possible.: Selecting inputs in order to produce a desired level of output at the lowest cost possible. 10. The general tendency for output to increase at a decreasing rate when additional amounts of an input are used in production, holding the amount of other inputs constant.: The general tendency for output to increase at a decreasing rate when additional amounts of an input are used in production, holding the amount of other inputs constant. 11. The amount by which total output increases when one more worker is hired.: The amount by which total output increases when one more worker is hired. 12. The amount of a good or service a firm produces.: The amount of a good or service a firm produces.