When Detailing the Cost of Producing Electricity with Turbines of Different

When detailing the cost of producing electricity with turbines of different sizes.The concept of scale economies is realized when:

A) the average cost tend to decrease as the size of the turbine decreases.
B) the average cost tend to increase as the size of the turbine decreases.
C) the average cost tend to decrease as the size of the turbine increases.
D) the average cost tend to increase as the size of the turbine increases.