Duolingo has the wrong gender. It should be el banco. My mother-in-law worked for the "Banco Central de Venezuela.
There is a whole other discussion on 'bancA' being the bench and 'bancO' being the bank. I am lost on this one.
It´s even more confusing, I´m afraid...¨banco¨ and ¨banca¨ can both be used in the money sense: http://forum.wordreference.com/showthread.php?t=178064
If we time travel back far enough, banking was done over a bench with the money man on one side and the customer on the other. So when you went to the bank, you were actually going to transact business over a bench. You can find evidence for this in both old German and Italian. And a small aside on banking. I think it was Carlos IV or V (not sure of the details) that wanted to be the Holy Roman Emperor. To raise an army to enforce his claim he went to the House of Welser (a German Banking House) to borrow the necessary funds. When he attained his goal he was out of funds to pay the bankers. His position gave him claim to what is now Venezuela. So Carlos said to the bankers, if you cancel my debt I will give you rights to explore this unknown area in the new world. He hinted at cities of gold etc. The Welsers had two sons who main talents were dueling, drinking and wenching so to get them out of Germany they made these two rowdies the leader of a group of Spanish conquistadors and off they went. They spent two years sick and starving in swamps and jungle and eventually the Spanish killed the German and nobody made bank.