How does selective breeding result in desired traits?

Selective breeding only mates two organisms that share the same desired trait, so that their offspring is guaranteed to have them.

For example, a dog with longer legs is more desirable than a dog with short legs.

The scanner should be purchased today.

Explanation:

Note: See the attached file for the calculations.

The net present value (NPV) of purchase is positive at $168.28,  while the present value of waiting to buy it in 10 years time is negative at $38.88.

This implies that a benefit of $168.28 would be realized if the asset is purchased today, while cost of $38.88 will be incurred if we wait.

Based on the benefit of $168.28 as against the cost of $28.88, the scanner should be purchased today.