Juscelino Kubitschek, President of Brazil from 1956 to 1961, ordered the construction of Brasília, fulfilling the promise of the Constitution and his own political campaign promise. Building Brasília was part of Juscelino's "fifty years of prosperity in five" plan. Lúcio Costa won a contest and was the main urban planner in 1957, with 5550 people competing. Oscar Niemeyer, a close friend, was the chief architect of most public buildings and Roberto Burle Marx was the landscape designer. Brasília was built in 41 months, from 1956 to April 21, 1960, when it was officially inaugurated.

Answer this question, if possible (if impossible, reply "unanswerable"): When was Brasilia inaugurated?
April 21, 1960