A district may issue negotiable promissory notes pursuant to this section to acquire funds for any district purposes. The maturity of the promissory notes shall not be later than five years from the date thereof. The total aggregate amount of the notes outstanding, at any one time, may be at least equal to seventy-five thousand dollars ($75,000) in any district but shall not exceed the lesser of either five million dollars ($5,000,000) or 3 percent of the assessed valuation of the taxable property in the district or, if the assessed valuation is not obtainable, 3 percent of the county auditor’s estimate of the assessed valuation of the taxable property in the district evidenced by his certificate . Promissory notes issued pursuant to Section 71812 may be disregarded in computing the aggregate amount of notes that may be issued pursuant to this section.