Valuation of preferred stock

In the course material, it is stated that preferred stocks are valued as below.

1. Highest 2 ratings of redeemable preferred stock: Purchase Price + Acquisition cost.

2. Highest 2 ratings of perpetual preferred stock: Fair Value

3. Lower rated redeemable and perpetual preferred stock: min (Book value, Fair Value)

But what is the RATIONALE for this? Can VA or someone throw some light on this?


Valuation of preferred stock