Suppose That a Firm,operating Efficiently,doubles the Size of Its Operations

Multiple Choice

Suppose that a firm,operating efficiently,doubles the size of its operations and discovers that,as a result,its average cost of production has fallen.What does this imply?

A) Decreasing returns to scale are present.
B) Increasing returns to scale are present.
C) Constant returns to scale are present.
D) No conclusion about returns to scale can be made.