Answer:
$75
Explanation:
A perfect competition is characterised by many buyers and sellers of homogenous goods and services. Market prices are set by the forces of demand and supply. There are no barriers to entry or exit of firms into the industry.
In the long run, firms earn zero economic profit. If in the short run firms are earning economic profit, in the long run firms would enter into the industry. This would drive economic profit to zero.
Also, if in the short run, firms are earning economic loss, in the long run, firms would exit the industry until economic profit falls to zero.
The price per unit = $300 / 60 = $5
The marginal revenue for one unit is $5
Production increased by 15 units, so marginal revenue increased by $5 × 15 = $75
I hope my answer helps you
