Can an unused and expired h1b visa be extended or transferred ?

Employer A filed for my H1B visa which got stamped on 8th of April 2013 and got expired on 14th January, 2014. During this period I could not go to US and the visa remained unused. The following are my queries:

1. Can employer A file for an extension of my visa now ?

2. If I switch to employer B, can my visa be transferred to Employer B ?

 

Thanks,

Nand