Southwest Airlines, a consistently profitable airline, describes itself as a low$-$ fare carrier with the highest level of customer service and with fun added to the airline. From a marketing perspective this statement could be interpreted as evidence of supporting one of the following observations more than the other three. Which one of the following observations is best described by this statement?

a$.$ Marketing is a symbiotic exchange between Southwest Airlines and its customers.

b$.$ Marketing at Southwest Airlines is about generating profit.

c$.$ Marketing at Southwest Airlines is concerned only with keeping customers happy.

d$.$ Marketing at Southwest Airlines focuses primarily on serving customers who cannot afford high$-$priced tickets.