Explanation:

- Train P crosses an electric pole in 30 seconds, so its speed is calculated by its length divided by time.

- It also crosses a 200-meter long tunnel in 40 seconds.

- Let L be the length of Train P and S the speed.

- Thus, $S=\frac{L}{30}$ and $S=\frac{L+200}{40}$.

- Solving $\frac{L}{30}=\frac{L+200}{40}$, we find $L=200$ meters.

- Speed of Train P, $S=\frac{200}{30}\times 18/5\text{ m/s}=24\text{ m/s}$.

- Train Q's speed is 18 km/h more than Train P.

- Converting speeds to m/s, $Q=(24+\frac{18\times 5}{18})\times 5/18\text{ m/s}=29\text{ m/s}$.

- Distance when crossing each other: $L_P+L_Q=(24+29)\times 20=1060$ meters.

- So, $L_Q=1060-200=860$ meters.

- ?? Except the calculated value is not an option available.

- Re-calculate speed in km/hr and account exact calculation twists or let cross-verification as needed.