Ignore something so chucklesome? I should cocoa! If you want your revenge, what about presenting your "correspondent" with an invoice from a "supplier" for investigating the equation? I could organise one for you, if you're prepared to give a snail or e mail address (dropbox via /msg acceptable). Valid business details & VAT number can be included for added verisimilitude. I'd ask you to suggest the amount, as you will know best how much will maximise revenge while retaining credibility. If you go down this route, with or without my assistance, do let us know what happened.