Why are firms so obsessed with the pricing element of the marketing mix?

a. Because pricing is the most difficult element of the marketing mix to change.
b. Because it is considered to be one of the few ways to differentiate a product in commoditized and mature markets.
c. Because pricing is the only marketing element that matters to customers.
d. Because pricing is the best part of the marketing mix in which to make an educated guess about the most appropriate strategy.
e. Because pricing is directly responsible for demand.