41.   For reasons linked to the physical strength needed to operate them at the beginning, spinning mules were operated by men.

42.   This can occur if plants are operating at less than minimum efficiency scale.

43.   It is also necessary for the firm to be operating at above minimum efficiency scale, the low point of the average cost curve.

44.   If the firm is operating at MES, the opportunity to expand output will not result in lower costs.

45.   The Cecchini Report finds evidence that many plants in Europe operate at less than MES.

46.   This is determined by the gradient of the average cost curve, and by the degree to which plants are operating at less than MES.

47.   The figure shows that the cost disadvantage of operating at half MES depends upon the gradient of the average cost curve.

48.   The system operating at LIFFE, called delta based margining, is more complex.

49.   These factors clearly operate at different scales.

50.   A laser necessarily operates at a frequency such that the total mistuning is equal to zero.