Use the level-payment mortgage formula:

$$PMT = PV \cdot \frac{r}{1-(1+r)^{-n}}$$

where:

• $PV = 100{,}000$
• $PMT = 740$
• $n = 15 \times 12 = 180$
• $r$ is the monthly yield.

Solving for $r$ gives a monthly rate of about 0.333%, which annualizes to about 4.0% nominally compounded monthly.

So the closest answer is A. 4.0%.