Congress passes a law that employers must give employees up to 12 weeks unpaid leave to attend to ...

Congress passes a law that employers must give employees up to 12 weeks unpaid leave to attend to family matters. The Virginia legislature decides that this in not enough and passes a law that requires employers in Virginia to provide 16 weeks unpaid leave. This law is likely:
 a. unconstitutional because its terms are different from those of the federal law
  b. unconstitutional because employee relations is a strictly federal area of concern
  c. constitutional as long as the law does not unnecessarily impede interstate commerce because it strengthens the federal law
  d. constitutional because states may regulate businesses in their borders in whatever manner they think appropriate
  e. unconstitutional because it invades the police power of the federal government