The following table shows the quantity and the long-run total cost of a firm

Quantity (thousands) 1 2 3 4 5 6 7 8 9 Long-run total cost (thousands of dollars) 50 80 111 140 170 216 273 336 468 a. At what level(s) of quantity are there economies of scale? Explain your answer. b. Discuss three factors that create economies of scale.