a) Percentage rate of return
b)Is the firm earning an economic profit.
The firm is earning an economic profit because it is a competetive firm and competetive firms earn economic profits in the short run.
c).In the short run the firm will see entry while in the long run they will see exit
d.)In the long run ,the economic profit will be equal to zero.In a competitive firm , the long run the the average revenue will be equal to the marginal revenue