Answer:
They are currently earning an economic profit of $1,600 per year
Explanation:
Economic profit = total revenue - accounting costs - opportunity costs
in this case:
opportunity costs = interest earned by their bond investment + the salaries of the three sisters = ($120,000 x 7%) + ($35,000 x 3) = $8,400 + $105,000 = $113,400
accounting costs = $25,000
total revenue = $140,000
Economic profit = $140,000 - $25,000 - $113,400 = $1,600