A (3.6500 g) of impure ammonium aluminium sulfate (NH₄Al(SO₄)₂)) was treated with ammonia (NH3(aq)) producing hydrous alumina Al₂O₃.xH₂O. The collected precipitate was filtered, washed, and ignited at 1000 C to give 0.4935 g Al₂O₃ (Mw 101.9635 g/mol). Determine:

a. % Al₂O₃. (2 Marks)

b. %Al. (3 Marks)

c. Express concentration of Al in ppm. (2 Marks)