Which ones are correct regarding top-down estimates in project management?

Top-down estimates (You may select more than one answer. Single click the box with the question mark to produce a check mark for a correct answer and double click the box with the question mark to empty the box for a wrong answer. Any boxes left with a question mark will be automatically graded as incorrect.) are used in the project conceptual phase depend on surrogate measures such as weight or square feet or ratios do not consider individual activity issues and problems are good for rough estimates can help select and prioritize projects are made by people familiar with the task help to gain buy-in on the validity of the estimate improve the accuracy of the estimate should be preferred if estimating cost is reasonable