Bandwidth is defined as a frequency span - the difference between a high frequency and a lower frequency. For the low end voice it depends if its male bass bariton tenor or female alto and soprano. A...
The USPS has a calculator on their website where you can select a destination, shape, and weight of package. http:/ircalc.usps.gov
For me, a postcard from the Midwest U.S. to Europe cost roughly...