Choice B is the correct answer. Let $p$ = plane speed in still air and $w$ = wind speed.

System: Distance = Speed × Time $\begin{cases} (p + w) \cdot 2 = 600 \\ (p - w) \cdot 3 = 600 \end{cases}$

Step 1: Simplify: $\begin{cases} p + w = 300 \\ p - w = 200 \end{cases}$

Step 2: Add equations: $2p = 500$$p = 250$

Step 3: Find $w$: $250 + w = 300$$w = 50$

Solution: Wind speed is 50 mph

Verification: With wind: $(250 + 50) \times 2 = 600$ ✓, Against: $(250 - 50) \times 3 = 600$ ✓

💡 Strategic Tip: Wind/current helps in one direction, opposes in the other.

Choice A is incorrect because with $w = 40$: plane speed would be 260, and return trip would be $220 \times 3 = 660 \ eq 600$.

Choice C is incorrect because with $w = 60$: plane speed would be 240, and return trip would be $180 \times 3 = 540 \ eq 600$.

Choice D is incorrect because with $w = 75$: plane speed would be 225, and return trip would be $150 \times 3 = 450 \ eq 600$.