On a graph where the total income is on the horizontal axis and the number of tasks is on the vertical axis, why does the piece rate appear as a straight line? Show that if the piece rate goes up, the line becomes flatter. What would the following contracts look like on the same graph, with the same axes?

(a) A contract that pays 10 pah a bushel for the first 20 bushels, followed by 20 pah a bushel for each additional bushel.

(b) A contract that pays a flat wage of 100 pah, plus 10 pah per bushel.

(c) A contract that pays 200 pah and requires you to harvest at least 20 bushels.