A financial institution shall compute its net earnings: based on the accounting period used as its fiscal year; and subject to the modifications required under this section, in the manner that a corporation computes, for purposes of the income tax, the Maryland modified income. A financial institution shall add to its net earnings computed under subsection (a) of this section the amounts that, even if otherwise allowed to be subtracted under § 10–307(b) and (g)(1) and (4) of this article, equal: profit realized from the sale or exchange of bonds issued by this State or a political subdivision of this State; dividends received from foreign corporations and included in federal gross income under § 78 of the Internal Revenue Code; interest derived from a United States obligation; State tax–exempt interest received from a mutual fund and allowed to be subtracted under § 10–307(g)(4) of this article; and interest excluded from federal gross income under § 103 of the Internal Revenue Code and derived from a bond: issued by a state or a public corporation, special district, or political subdivision of a state or their instrumentalities; or under § 150 of the Internal Revenue Code, treated as a bond issued by a state or a public corporation, special district, or political subdivision of a state or their instrumentalities. A financial institution shall subtract from its net earnings computed under subsection (a) of this section interest expense incurred to purchase or carry a bond as defined in subsection (b)(5) of this section.