**iii) Total Cost Curves: **Let us begin with a picture of Total Cost, Total Fixed Cost and Total Variable Cost Curves. This is simpler and easier to understand. With increasing units of output: 4, 11, 18, 23, 25 and 26, Total Fixed Cost remains constant at $40. Total Variable Cost increases proportionately as 10, 20, 30, 40, 50 and 60. The Total Cost as a sum of the two (Total Fixed and Total Variable Costs) increases as 50, 60, 70, 80, 90 and 100. In the figure three cost curves have been drawn accordingly.

Total Output Units have been measured along the horizontal axis and Total Costs have been shown on the vertical axis. At a distance of 40 units we find T - FC as a line parallel to OX axis. This shows that even at zero output level TC is equivalent to FC. From here onwards TC rises continuously and in the same proportion as VC. Therefore VC and TC are parallel curves.

**iv) Marginal, AVC, AFC, ATC, curves:** Let us now turn to the slightly complex nature of the marginal and average cost curves.

a) Marginal and Average Cost Curves: In Figure 29 we have once again shown varying output units on the horizontal axis and different cost amounts on the vertical axis. All the four cost curves have been drawn on the basis of respective values in the tables above. Marginal Cost varies as 2.5, 1.42, 1.42, 2.0, 5.0 and 10.0. Accordingly the Marginal Cost Curve has been drawn. It shows an initial downward trend but a subsequent sharp rise. AFC is based on the values 10, 3.63, 2.22, 1.73, 1.60, 1.54 therefore it is seen to be continuously falling. However, initially it falls sharply and then with a slower tempo. AFC first falls sharply and then its curve becomes flatter. AVC is based on the cost values 2.5, 1.82, 1.67, 1.73, 2.0 and 2.33. Therefore AVC initially falls moderately and then it rises continuously but moderately. Since ATC is combination of both AFC and AVC, it has a mixed behavior. It is based on the values 12.5, 5.45, 3.89, 3.46, 3.60 and 3.80. The behavior of ATC is to be explained in terms of the joint behavior of AFC and ATC. It is necessary to analyze ATC more carefully. Let us workout its features.

**b) Behavior of ATC:** Certain features of the ATC are worth analyzing. These are as follows: