Ans:
(a) The waterfall model seems an ideal choice here. No other model seems a reasonable alternative to accept as a different answer.

Strengths

1. The company is large and bureaucratic, requiring documentation and good project visibility. Waterfall documentation satisfies this.
2. The company has a high staff turnover. So probably many employees are new and inexperienced. Waterfall works well with inexperienced staff.
3. The application type is well known to the company, so a thorough user requirements analysis should be possible early on.
4. An existing application is to be re-engineered. This also confirms that the user requirements are known early. They could be extracted from the existing application.
5. The company will maintain the software, so good documentation will be essential.
6. The company has a good reputation to maintain in this area, so quality control will be essential. Waterfall emphasis of requirements-before-design and design-before-coding will emphasise quality.

Weaknesses

Waterfall has no obvious weaknesses on this project.

1. We may end up swimming upstream, but the chances seem minimal since the requirements should be clear from the start.
2. Late arrival of code may be one, but on the other hand our client may be able to continue using the existing application until the new system arrives.