By mid-1788, Mozart and his family had moved from central Vienna to the suburb of Alsergrund. Although it has been suggested that Mozart aimed to reduce his rental expenses, research shows that by moving to the suburb, Mozart had not reduced his expenses (as he wrote in his letter to Puchberg), but merely increased the housing space at his disposal. Mozart began to borrow money, most often from his friend and fellow mason Michael Puchberg; "a pitiful sequence of letters pleading for loans" survives. Maynard Solomon and others have suggested that Mozart was suffering from depression, and it seems his output slowed. Major works of the period include the last three symphonies (Nos. 39, 40, and 41, all from 1788), and the last of the three Da Ponte operas, "Così fan tutte", premiered in 1790.