How much should I charge for audio post production work?

So a UK company is hiring me for some audio work (mostly syncing and mastering). He said it'll only be a few hours of work.

How much should I charge? Should it be by the day? By the hour? By minute of audio?

I'm doing this today at like 2pm CST, so quick responses are preferred.

ONE MILLION POUNDS

http://www.goldstreet.net/RatesAV.html

call these guys and tell them the same details you got and ask for a quote:

http://www.stuckonon.com/

  On 5/2/2012 at 7:53 PM, chenGOD said:

http://www.goldstreet.net/RatesAV.html

 

call these guys and tell them the same details you got and ask for a quote:

http://www.stuckonon.com/

Bitch told me that they worked hard to find out their rates and refused to tell me. I just called some other places and said I was a prospective client. They all had hourly rates though, and those rates reflected the fact that they have badass studios.

The guys asked me for a day rate, so I just went ahead and said $150. Hope I'm not underselling myself.