Temporary Employment Corporation (TEC) places temporary workers in companies during peak periods. Here is a description of the business:

- **Candidates**: TEC maintains a file of candidates willing to work. Each candidate can have a job history if they have worked before. Candidates have various qualifications, and each qualification may be shared by multiple candidates.

- **Companies**: TEC has a list of companies that request temporary workers.

- **Openings Folder**: Every time a company requests a temporary employee, TEC creates an entry in this folder. Each entry includes:
- Opening number
- Company name
- Required qualifications
- Starting date
- Anticipated ending date
- Hourly pay
Each opening requires one specific qualification. When a candidate matches the required qualification, they are assigned the job.

- **Placement Record**: An entry is made in this folder when a candidate is placed in a job. It includes:
- Opening number
- Candidate number
- Total hours worked, etc.
Additionally, an entry is made in the candidate's job history.

- **Special Codes**: TEC uses special codes to describe a candidate's qualifications for an opening.

Task: Construct an Entity-Relationship (E-R) diagram using Chen's model to represent these requirements. Ensure to include all appropriate entities, relationships, attributes, and cardinalities.