For the purposes of the formula:(1) the letter A represents the total of the sums to be apportioned under the first part and the second part of the municipality eligible under the third part;
(2) the letter B represents the total of the sums to be apportioned under the first and second part of all the municipalities eligible under the third part;
(3) the letter C represents the sum to be apportioned under the third part, in accordance with section 18.