As a term and condition of doing business, you set the rule of commerce in your domain. For example;
" We accept Bitcoin only" and offer the means to exchange their money of exchange into bit coin.
At the rate of that moment in time.
Printed copy · Anthology Volume 3, page 450Printed copy from The Tender For Law Anthology, Volume 3, page 450 (printed 13 June 2014). Added by this site; not part of the Facebook export.