Two parallel rail tracks run north-south Train `A` moves north with a speed of `54 km h^(-1)` and train `B` moves south with a speed of `90 km h^(-1)`. What is the
a. relative velocity of `B` with respect to `A`?
b. relative velocity of a monkey running on the roof of the train `A` against its motion (with its velocity of `18 km h^(1)` with respect to the train `A` ) as observed by a man standing on the ground?

Explanation

To solve the problem step-by-step, we will break it down into two parts as per the question.

### Part (a): Relative Velocity of Train B with Respect to Train A

1. **Identify the velocities**:
- Train A moves north at a speed of \(54 \, \text{km/h}\).
- Train B moves south at a speed of \(90 \, \text{km/h}\).

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