Answer: Marginal cost is $27 and market price is $27
Explanation:
In the long run, perfectly competitive industries make zero economic profit. This means therefore that Average cost will be the same as the Market price so Market price will be $27.
Firms in a perfectly competitive industry will produce at a rate where Marginal revenue will equal marginal cost in order to maximise profit.
In a perfectly competitive industry, firms are price takers which means that the Market price is also the same as the Marginal revenue. The Market price will therefore be equal to marginal cost which means that Marginal cost will also be $27.