单选题 Samantha has been working for a law firm and earning an annual salary of $90,000. She decides to open her own practice. Her annual expenses will include $15,000 for office rent, $3,000 for equipment rental, $1,000 for supplies, $1,200 for utilities, and a $35,000 salary for a secretary/bookkeeper. Samantha will cover her start-up expenses by cashing in a $20,000 certificate of deposit on which she was earning annual interest of $1,000. Assuming that there are no additional expenses, Samantha's annual implicit costs will equal