The issuance of bonds is authorized when, at a bond election, any of the following occurs:
(a)
Two-thirds of the votes cast on the proposal are “yes.”
(b)
A majority of the votes cast on the proposal are “yes” when the election was called pursuant to a petition sufficient to require it to be called.
(c)
A majority of the votes cast on the proposal are “Yes” when the bonds to be issued are payable both as to principal and interest solely from revenue and not directly or indirectly from assessments and the board finds that in its judgment the proposed revenues will each year, after deducting a reasonable allowance for the cost of operation and maintenance, if any, which must be paid from the revenues, be at least one and one-tenth times the debt service requirements for that year for principal, interest, sinking funds and reserve funds of all the bonds, including the bonds to be issued, payable from the revenues.