The conversion will be done automatically by your bank, with the current exchange rate. You will get a discount of 19.6% as you don't have to pay the VAT though.
Hofstadter's Law: "It always takes longer than you expect, even when you take into account Hofstadter's law."
But you should add 33% to price ( VAT deducted ) because of the change rate : 1 euro = 1.33 US $
So , as PhilThib said , it's nearly 43-45 US $. (39.99-19.6%)*1.33