Two cars `A and B` are moving west to east and south to north, respectively, along crossroads. A moves with a speed of `20 m s^-1` and is `500 m` away from the point of intersection of cross roads and `B` moves with a speed of `15 ms^-1` and is `400 m` away from the point of intersection of cross roads. Find the shortest distance between them.

Explanation

To find the shortest distance between the two cars A and B, we can follow these steps:

### Step 1: Understand the motion of the cars
- Car A is moving from west to east with a speed of \(20 \, \text{m/s}\) and is \(500 \, \text{m}\) away from the intersection point (let's call it point O).
- Car B is moving from south to north with a speed of \(15 \, \text{m/s}\) and is \(400 \, \text{m}\) away from point O.

### Step 2: Set up the coordinate system
- Place point O (the intersection) at the origin \((0, 0)\).
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