A theatre company engages a lead actress to perform in a new West End production running for eight weeks. The contract requires her to be present for the opening night and all subsequent performances. Two days before opening night, the actress informs the company that she cannot attend the first week of performances due to a family emergency. The theatre company wishes to terminate the contract and hire a replacement immediately.
Which of the following best describes the classification of the term requiring the actress to perform from opening night?