Ralph is single and has the following items for the current year:

Nonbusiness capital gains $ 9,000
Nonbusiness capital losses (3,000)
Interest income 6,000
Itemized deductions (none of the amount resulted from a casualty loss) (10,000)

In calculating Ralph's net operating loss, and with respect to the above amounts only, what amount must be added back to taxable income (loss)?
a. $4,000
b. $0
c. $3,000
d. $2,000
e. None of these choices are correct.