A firm in a monopolistically competitive market is usually indifferent to an additional customer walking through the door, since a sale to that customer will not increase the firm's profit.

Monopolistically Competitive

Pertaining to a market structure where many firms sell products that are similar but not identical, allowing for some degree of market power due to product differentiation.

Indifferent

A state of having no particular interest or sympathy; unconcerned or having no preference.

Additional Customer

Refers to a new or extra consumer who purchases or is likely to purchase goods or services from a business, contributing to the firm's customer base growth.