Conversation so far:
what happened in 2011?
On November 11, 2011, it was revealed that Vampire Weekend had been in the studio, writing and recording material for their third album
when did Vampire Weekend release the album?
Modern Vampires of the City by vampire weekend was released in May 2013
was the album Modern Vampires of the City by vampire weekend was released in May 2013 a success?
the album Modern Vampires of the city by vampire weekend debuted at #1 on the Billboard chart

Question: how many copies were sold?
Self-contained rewrite: how many copies the album Modern Vampires of the city by vampire weekend debuted at #1 on the Billboard chart were sold?