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As a US citizen visiting a Schengen country it is very likely you will not even be asked about money, but you might be and in that case you better show you have a credit card which will cover the needed money for a hotel, or the last few bank statements which show your monthly income coming in, and/or a savings account that holds enough money.
It is again very unlikely that you will need the money for staying in a hotel and eating out three times a day, and you may want to look up a hostel in the area if you do not have a regular income which will cover that much money.
So if you are challenged on the amount of money you explain that you expect to stay with your friend and if something happens, you are planning to use a hostel instead, (with the added benefit that you can cook your own meals from supermarket supplies.)
But it is the best to have those 2040€ in your bank and/or savings account.
(If you can not have 2500US$ in your accounts, can you afford to travel to Europe?)