(b)
Taxable income from sources without United States
From the items of gross income specified in subsection (a) there shall be deducted the expenses, losses, and other deductions properly apportioned or allocated thereto, and a ratable part of any expenses, losses, or other deductions which cannot definitely be allocated to some item or class of gross income. The remainder, if any, shall be treated in full as taxable income from sources without the United States. In the case of an individual who does not itemize deductions, an amount equal to the standard deduction shall be considered a deduction which cannot definitely be allocated to some item or class of gross income.