I agree it confusing.
If the firm uses its own money, the value of the assets increases by the NPV. In this case, 15 + 4 = 19.
Another way of seeing it is that the firm has a negative cashflow of -2 and then future cashflows with present value 6; hence, the value is 15-2+6=19
Debt increases because the firm would not have enough assets to pay the debt if the project is not implemented. Equityholders only get a benefit when the firm can pay the debt in at least one scenario.
If the firm uses its own money, the value of the assets increases by the NPV. In this case, 15 + 4 = 19.
Another way of seeing it is that the firm has a negative cashflow of -2 and then future cashflows with present value 6; hence, the value is 15-2+6=19
Debt increases because the firm would not have enough assets to pay the debt if the project is not implemented. Equityholders only get a benefit when the firm can pay the debt in at least one scenario.