Baccara

Baccara was a female vocal duo formed in 1977 by Spanish artists Mayte Mateos (7 February 1951, Logroño) and María Mendiola (4 April 1952, Madrid). The pair rapidly achieved international success with their debut single "Yes Sir, I Can Boogie", which reached number one across much of Europe and is one of the best-selling singles of all time. A successful follow-up single ("Sorry, I'm a Lady") and European tour led to a number of album releases, numerous television appearances and the duo's selection to represent Luxembourg in the Eurovision Song Contest 1978.

source: Wikipedia