21) (D) all of the above are true. Because at market price $9 no
buyer is willing to purchase because all buyers willingness to pay
is less than $9 so statement (A) is true.option (B ) is also true
because at $5.50 Megan is indifferent because his willingness to
pay is equal to this price so he is indifferent. Option (C) is also
correct because at $4 price consumer surplus is ($4.50 +$3 +$1.5)
is $9. So all statements are true,therefore option (D) is correct
answer.
22) Total cost = $1200
Total fixed cost = $200
Total variable cost(TVC) = 1200 - 200 =$1000
At 400 units Average variable cost = TVC/Q
Average variable cost = 1000/400 = $2.50
Therefore,option (B) is correct answer.
23) (C) Monopolistic competition.
In Monopolistic competition has all the given characteristics
i.e many firms, differentiated products, and free entry.
24) True , given statement is true i.e Free entry
eliminates long-run profits for firms in competitive and
monopolistic industries. Because in short run in both market has
some positive profit but as firm enter in the market reduces the
profit and in long run in both market profit will be zero.
25) False, Beacuse govt set a price more than equilibrium price
and if anyone sell the airline ticket at equilibrium price then he
face loss and no one want to face loss so no one sell at
equilibrium price.