[85] The two first of these variables are included in the _x_, and the two last in the _y_, of the formula given at p. 162 of "Unto This Last," and the four are the radical conditions which regulate the price of things on first production; in their price in exchange, the third and fourth of these divide each into two others, forming the Four which are stated at p. 186 of "Unto This Last." Now, in order to show the manner in which price is expressed in terms of a currency, we must assume these four quantities to be known, and the "estimate of desirableness," commonly called the Demand, to be certain. We will take the number of persons at the lowest. Let A and B be two labourers who "demand," that is to say, have resolved to labour for, two articles, _a_ and _b_. Their demand for these articles (if the reader likes better, he may say their need) is to be absolute, existence depending on the getting these two things. Suppose, for instance, that they are bread and fuel in a cold country, and let _a_ represent the least quantity of bread, and _b_ the least quantity of fuel, which will support a man's life for a day. Let _a_ be producible by an hour's labour but _b_ only by two hours' labour; then the cost of _a_ is one hour, and of _b_ two (cost, by our definition, being expressible in terms of time). If, therefore, each man worked both for his corn and fuel, each would have to work three hours a day. But they divide the labour for its greater ease.[86] Then if A works three hours, he produces 3_a_, which is one _a_ more than both the men want. And if B works three hours, he produces only 1-1/2_b_, or half of _b_ less than both want. But if A works three hours and B six, A has 3_a_, and B has 3_b_, a maintenance in the right proportion for both for a day and a half; so that each might take a half a day's rest. But as B has worked double time, the whole of this day's rest belongs in equity to him. Therefore, the just exchange should be, A, giving two _a_ for one _b_, has one _a_ and one _b_;--maintenance for a day. B, giving one _b_ for two _a_, has two _a_ and two _b_;--maintenance for two days. [86] This "greater ease" ought to be allowed for by a diminution in the times of the divided work; but as the proportion of times would remain the same, I do not introduce this unnecessary complexity into the calculation. But B cannot rest on the second day, or A would be left without the article which B produces. Nor is there any means of making the exchange just, unless a third labourer is called in. Then one workman, A, produces _a_, and two, B and C, produce _b_;--A, working three hours, has three _a_;--B, three hours, 1-1/2_b_;--C, three hours, 1-1/2_b_. B and C each give half of _b_ for _a_, and all have their equal daily maintenance for equal daily work. To carry the example a single step farther, let three articles, _a_, _b_, and _c_, be needed.