74. The value of a change is determined as follows:
(1) estimation, negotiation and acceptance of a detailed lump sum that takes into account, for the contractor’s overhead, administrative costs and profits, the markup percentage, as the case may be, in subparagraph a or b of subparagraph 3;
(2) if the nature of the change in the work is such that a lump sum cannot be estimated, application of the unit prices indicated in the contract or subsequently agreed on; or
(3) if the nature of the change is such that a lump sum or unit prices cannot be estimated, addition of the cost of labour, materials and equipment relating to the change and increased:
(a) by 15% if the work is performed by the contractor; or
(b) by 10% for the contractor and 15% for the subcontractor if the work is performed by a subcontractor.
For the purposes of subparagraph 3 of the first paragraph, the cost of labour, materials and equipment corresponds to the actual costs of the items listed in Schedule 6. The increase includes the contractor’s overhead, administrative costs and profits.