Answer:
Explicit Costs: 1500+1750 = 3250.
Explicit Cost is the cost that is tangible and can be seen.
Implicit Costs & Opportunity Costs: 20000+4000 = 24000.
Implicit cost and opportunity cost will be the same here because they both represent the intangible cost that is foregone by choosing the next best alternative.
Economic Profit: Revenue - Explicit Costs - Implicit Costs
Therefore, the economic profit in this question will be,
45000-3250-24000 = $17480.
Although Britney is earning a profit of $17480 in 2012, from economic viewpoint, she is operating at loss because she could have earned $24000(Rent+Music) by just doing what she was doing previously.
Hope my answer helps you. Good luck.