Sears' management failed to consider the effect of services not offered by Sears, such as second$-$day shipping, which was offered by some online retailers.

b$.$ This is an example of Sears failing to prepare for

$$ substitute services that would be appealing to Sears' customer base.

sellers using their bargaining power to offer services not available at Sears.

$$ the intensity of competition among existing competitors.

$$ buyers using their bargaining power to demand new services.