This year, Micah Smith paid $20,000 of interest on a mortgage on his home (Micah borrowed $600,000 in 2015 to buy the residence and it is currently worth $1,000,000), $12,000 on a $150,000 home-equity loan on his home, and $10,000 of interest on a mortgage on his vacation home at ski resort (loan of $300,000; home purchased for $400,000 in 2016; home is not rented out at any time).

How much interest expense can Micah deduct as an itemized deduction? Do tax research, what primary source supports Micah interest deduction on his homes?