Describe the role that extinction has played in biological evolution. Discuss how the current mass extinction of species differs from past mass extinction events, and the consequences of this current mass extinction.

Firms use marginal analysis to determine prices by a) changing prices in accordance with information from retailers. b) using comparisons with strong competitors to position prices accordingly. c) examining the effect on revenue of small changes to the price of one item. d) trying to minimize production costs by using better and more efficient methods.