A simple and related to math

1. If you have 128 kbps bandwidth through an ISDN Internet Connection; How many minutes will it take to download a 1MB file from the Internet Normally?

Please tell me the formula of finding out the answer as well;

Cheers;

TCPmag.com | Q and A: Calculating ISDN and OC48 Transfer Times (http://tcpmag.com/qanda/article.asp?EditorialsID=313)