No tax shall be imposed upon:
(a) Any person as to whom, or any occupancy as to which, it is beyond the power of the City to impose the tax herein provided;
(b) Occupancy of rooms by officers or employees of a legal entity which has a written lease upon said rooms for at least one (1) year, and which leased rooms are not available to the general public at all times during the lease period. Said rooms must exceed 50% of the total units in the facility to qualify for the exemption;
(c) No such exemptions shall be claimed or granted except upon a written claim therefor made under the penalty of perjury at the time rent is collected upon a form prescribed by the Tax Collector. Each operator shall file the claims or true copies thereof, with the Tax Collector with any return upon which exemptions are claimed; except that exemptions based upon a written lease, may be claimed by filing a true copy of said lease with the Tax Collector with the first return following execution of the lease, and making reference to it in each return thereafter during its term.