Given Scenario:

The scenario involves a unit price contract between the owner and the contractor.

A unit price contract stipulates that the owner will pay the contractor for the actual quantities used at the bid unit rates. Typically, the contractor agrees to perform at or below the bid unit rate, while the owner may account for the possibility that the quantities could exceed the estimated range. The scenario best fits with the concept that:

The contractor can perform at or below the bid unit rate.

The owner recognizes that quantities may vary but are expected to be within an estimated range.