When income rises, total expenditures remain constant

Minimum efficient scale is defined as the level of output at which

A) the firm's long-run average total cost starts falling. B) all economies of scale are exhausted. C) the maximum output is produced. D) diminishing returns affect average total cost.

Heteroskedasticity means that

A) homogeneity cannot be assumed automatically for the model. B) the variance of the error term is not constant. C) the observed units have different preferences. D) agents are not all rational.