In calculating return on investment (ROI), the use of book values of assetsparticularly fixed assetsin the ROI denominator

a.	is the preferable method.
b.	may cause a manager of a division with fully depreciated assets to be reluctant to replace the assets with more costly assets.
c.	is required by generally accepted accounting principles.
d.	may cause a manager of a division with fully depreciated assets to replace the assets with newer, more efficient, but more costly assets.