Tara, a pharmacist, is planning on opening her own pharmacy. Tara currently earns $$50,000$ a year at her job. She has calculated that it will cost her $$6,000$ in rent and utilities and $$25,000$ for an assistant per year to run her pharmacy. What is the amount of opportunity cost that Tara incurs in running her own pharmacy?

$$81,000$

$$31,000$

$$25,000$

$$50,000$