A national bank may collectively invest assets that it holds as fiduciary in:
A single real estate loan, a direct obligation of the United States, an obligation fully guaranteed by the United States, or a single fixed amount security, obligation, or other property, either real, personal, or mixed, of a single issuer; or
A variable amount note of a borrower of prime credit, if the bank uses the note solely for investment of funds held in its fiduciary accounts.