Answer:
The economic costs are the sum of the explicit costs or monetary costs, and the implicit costs, or opportunity costs.
The explicit or monetary costs that Felix has are:
Payments to manufacturer: $476,000
Wages and utility bills: $281,000
Total monetary costs: $751,000
The implicit or opportunity costs that Felix is incurring are:
Rent he would get for his showroom: $71,000
Salary he would get as an accountant: $34,000
Total opportunity costs: $105,000
Total economic costs: $751,000 + $105,000 = $856,000