[ubuntu] unable to startup iMac stuck CD

I installed refit on my 2006 iMac because I wanted to install Linux in dual boot. The CD I am using is stuck in the drive so when I start up my iMac, all I get is a white screen. Is there any way to force eject the CD, or, if I hook up my Mac bootable usb drive, can I force the Mac to boot from the USB drive so I can try and remove the CD?

Any other options please let me know. I really need to get this machine going but all I need to do is remove the CD or find a way to bypass the Mac on startup to start from the USB drive.