For the yer ended December 31, 2015, David, a married taxpayer filing a joint return, reported the following:

Investment income from interest : $ 24,000

Investment expenses other than and not including investment interest expense : $ 4,000

Interest expense on funds borrowed in 2005 to purchase investment property : $ 70,000

what is maximum amount that David can deduct in 2015 as investment interest expense?

a. $ 7,000

b. $ 20,000

c. $ 21,000

d. $ 24,000

e. None of the above