As part of an estate settlement mary received $1 million. she decided to use the money to purchase a small business in anywhere, usa. her business operates in a perfectly competitive industry. if mary would have invested the $1 million in a risk-free bond fund she could have earned $100,000 each year. she also quit her job with lucky. com inc. to devote all of her time to her new business. her salary at lucky. com inc. was $75,000 per year. how large would mary's accounting profits need to be to allow her to attain zero economic profit

Zero economic profit, in simple terms means break even point. It is a situation or point where total revenue of a company must be equal to total cost. This can be represented as:  
Total revenue-Total cost = 0 
 In this case, Mary's accounting profits need to be $175,000 so that she can attain zero economic profit. 
 Explanation: Investment made to business = $1 million which if Mary would have invested in risk-free bond, then she would have earned $100,000 per year. So, $100,000 is a cost. 
 Also, she left job(to devote time to business) from which she was earning $75,000 per year as salary. But as she left the job, this amount is also gone.
So, this is also a cost for her. 
 Now,
 Total cost = $100,000 + $75,000 = $175,000 
 To attain zero economic profit Mary' accounting profit should be $175,000.