Answer:
c the price elasticity of demand is about 1.43 and an increase in the airfare will cause airlines' total revenue to decrease.
Step-by-step explanation:
q1 2,000 p1 250
revenue1 = quantity x price = 2,000x250 = 500,000
q2 1,700 p2 280
revenue2 = 1,700 x 280 = 476,000
Midpoint formula:



Ep = -1.432432432
As the price elasticity is above -1 the decrease in quantity is greater than the decrease in price thus, the revenue of the firm decreases if increase the price.