Any American been to Turkey lately?

My daughter is going to Turkey in a week for her holiday. She was getting visa information and it states that for British Citizens it is $20, 15 euro or 10 pounds...for Americans it is $20 or 15 euro. It does not state £10 as an option.
They say you should bring the exact amount is wondering if she needs to get dollars of if they will give her an option of £10 which of course is less than $20. Anyone know?

Ha yes!
We didnt know this as we had £40 for 4 of us and then they saw my american passport and wanted 20 euro or 20 bucks...We explained I didnt have USD or EURO I lived in the UK and showed my visa...needless to say a bunch of BS and looking dumb the head guy took the pounds and gave me my sticker....
Bring exact cash

PS: they also were asking for an American credit card which of course I don't carry so they WILL get the money.

It was a great vacation though ;-)

Thanks! She will probably just get $20 ahead of time then..she doesn't want it to be a big deal (she is only 20 travelling with british friends the last thing she want is to be the one that has a problem)