In an auction, potential buyers compete for a good by submitting bids. adam galinsky, a social psychologist at northwestern university, compared ebay auctions in which the same good was sold. he found that, on average, the higher the number of bidders, the higher the sales price. for example, in two auctions of identical ipads, the one with the higher number of bidders brought a higher selling price. according to galinsky, this explains why smart sellers on ebay set absurdly low opening prices (the lowest price that the seller will accept), such as 1 cent for a new ipad. use the concepts of consumer and producer surplus to explain galinsky’s reasoning.

Kendra knight took part in a friendly game of touch football. she had played before and was familiar with football. michael jewett was on her team. in the course of play, michael bumped into kendra and knocked her to the ground. he stepped on her hand, causing injury to a little finger that later required its amputation. she sued michael for damages. he defended on the ground that she had assumed the risk. kendra claimed that assumption of risk could not be raised as a defense because the state legislature had adopted the standard of comparative negligence. what happens if contributory negligence applies? what happens if the defense of comparative negligence applies?