Explain the following variation order, query sheet, preambles, working up, defects liability period, give 6 main purposes of making Bill of quantities ?

Variation Order: A variation order is a document issued by the client or the main contractor to authorize changes to the original scope of work in a construction project. This could include changes in design, materials, or specifications, and may result in adjustments to the contract sum and/or the project timeline.

Query Sheet: A query sheet is a document used to raise questions or seek clarification on specific aspects of the project, such as design details, specifications, or contract terms. It is typically used during the tendering process or throughout the construction phase to ensure that all parties involved have a clear understanding of the project requirements.

Preambles: Preambles are introductory statements or clauses included in a contract or specification document that provide context, background information, or general guidelines for interpreting the rest of the document. They often outline the scope of work, responsibilities of the parties involved, and any specific conditions or requirements that apply to the project.

Working Up: Working up refers to the process of preparing detailed estimates or quantities from preliminary or approximate data. This may involve taking off quantities from drawings, calculating costs, and preparing schedules or bills of quantities to determine the overall scope and cost of the project.

Defects Liability Period: The defects liability period is a specified period of time after the completion of a construction project during which the contractor is responsible for rectifying any defects or issues that arise. This period is typically outlined in the contract and gives the client assurance that any problems will be addressed by the contractor.

6 main purposes of making Bill of Quantities:
1. To provide a detailed breakdown of the quantities of materials, labor, and equipment required for the construction project.
2. To assist in the preparation of accurate cost estimates and budgets for the project.
3. To facilitate the tendering process by providing a clear and consistent basis for contractors to submit their bids.
4. To serve as a basis for valuing variations and assessing progress payments throughout the construction phase.
5. To help in monitoring and controlling costs during the construction process.
6. To provide a reference document for measuring and valuing work done, as well as for resolving disputes or claims related to quantities or costs.