(a) Consolidation of claims. Where a debt is incurred for labor or materials furnished continuously by the same claimant for work upon a single improvement but under more than one contract, the claimant may elect to file a single claim for the entire debt. In such case, “completion of the work” shall not be deemed to occur with respect to any of the contracts until it has occurred with respect to all of them.

(b) Apportionment of claims. Where a debt is incurred for labor or materials furnished by the same claimant for work upon several different improvements which do not form all or part of a single business or residential plant, the claimant shall file separate claims with respect to each such improvement, with the amount of each claim determined by apportionment of the total debt to the several improvements, and in such case, the amount of each separate claim may be less than five hundred dollars ($500), provided that the total debt exceeds five hundred dollars ($500). In no other case shall an apportioned claim be allowed.