Temporary Employment Corporation (TEC) places temporary workers in companies during peak periods. TEC's manager provides the following business description:

- TEC maintains a file of candidates who are willing to work.
- If a candidate has worked before, they have a specific job history.
- Each candidate possesses several qualifications.
- Each qualification may be held by more than one candidate.

TEC also maintains a list of companies that request temporary workers. When a company requests a temporary employee, TEC records an entry in the openings folder. This folder includes:

- Opening number
- Company name
- Required qualifications
- Starting date
- Anticipated ending date
- Hourly pay

Each opening requires one main qualification. When a candidate matches the required qualification, they are assigned the job, and an entry is made in the Placement Record folder. This folder contains:

- Opening number
- Candidate number
- Total hours worked
- Additional relevant details

Furthermore, an entry is made in the candidate's job history. TEC uses special codes to describe a candidate's qualifications for an opening.

**Task**: Construct an E-R diagram based on Chen's model to represent the above requirements. Include all appropriate entities, relationships, attributes, and cardinalities.