In computing the annual tax there shall be deducted from the gross income the following items:
   A.   The amount of credit losses and uncollectibles actually sustained by the taxpayers;
   B.   Amounts derived from transactions in interstate or foreign commerce or from any business which the city is prohibited from taxing under the constitutions of the United States or the state of Washington;
   C.   Gross income derived from the sale of electricity, natural gas, cable television services and network telephone services to a single consumer in any monthly period to the extent that inclusion of such gross income would cause the tax attributable to gross income derived from such single consumer in such monthly period to be in excess of fifty dollars ($50.00). (Ord. 861, 1-30-2008, eff. 2-3-2008)