(a) If a resolution has been adopted pursuant to Section
2131, the board of directors shall:
   (1) Determine the total amount of revenue required by the district
which will be derived from an ad valorem tax or ad valorem
assessment on property on the secured roll.
   (2) Divide the amount determined pursuant to paragraph (1) among
the counties in which the district is situated in the proportions
that the estimated full values of taxable property on the secured
roll within the district in the respective counties bear to the
estimated total full value of such property within the district.
   (b) The estimated full value shall be determined by adding the
figures for the several counties.