100%Equity
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EBIT: $200,000
Interest: $0
Taxes: ($80,000)
EAT: $120,000
Equity: $1,000,000
ROE12.0%
50% Debt
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EBIT: $200,000
Interest: ($40,000)
Taxes: ($64,000)
EAT: $96,000
Equity: $500,000
ROE: 19.2%
This is my thought and is contingent on interest expense being tax deductible to the corporation.
Under the equity scenario. Taxes are $80,000 or 40% of $200,000 which is 20% of the $1mm asset base. So the $120,000 earnings after tax divided by the $1mm base is 12%
With 50% leverage, you deduct $40,000 (8% of $500,000 financing) and taxes on remaining amount. The new equity base is smaller at $500,000 so the ROE is higher at 19.2%.