Explanation:

- Let's define the distance between stations A and B as \(d\) km.

- The travel time from A to B at 40 km/h is \(t_1 = \frac{d}{40}\).

- The travel time from B back to A at 30 km/h is \(t_2 = \frac{d}{30}\).

- According to the problem, the total travel time is 6.3 hours:

$$

\frac{d}{40} + \frac{d}{30} = 6.3

$$

- To solve for \(d\), we find a common denominator (120):

$$

\frac{3d}{120} + \frac{4d}{120} = 6.3

$$

$$

\frac{7d}{120} = 6.3

$$

- Solving for \(d\), we get:

$$

7d = 6.3 \times 120

$$

$$

7d = 756

$$

$$

d = \frac{756}{7} = 108

$$

- Option 2: 108 km is the correct answer.

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