Jessica is a young doctor who has just started her own practice. Her previous position paid her $80,000 a year. For office space, she uses a building which she owns and which she has rented in the past for $40,000 a year. Her total revenue from her new practice is $250,000. She pays $50,000 to other firms for materials and supplies, and she pays $40,000 in wages to her office nurse. Assume that Jessica's building and equipment do not depreciate and that her normal profit is $20,000. a) What is the opportunity cost of all factors of production employed by Jessica? (5 marks) b) What is Jessica's economic profit?