What is required when the work is specified by the actual task (e.g., depth or length)?

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If the work is quantified by the actual task, viewing the location beforehand is mandatory because locations vary significantly in hardness and ease of digging, which cannot be precisely defined by description alone. The required dimensions, such as the circumference of the well, its depth, or the length and width of the river, must be known because these factors affect the labor involved.