3. (a) Explain what is meant by Formal Specification and Verification and describe a significant advantage of each. Mention a disadvantage that applies to both. Mention two situations where this approach to software development would be suitable. (b) Given the following diagram which shows hardware reliability over time, draw similar diagrams which express software reliability for both the idealised and the actual situations. Comment on the shape of the curves drawn and why they differ from the hardware curve below. Burn in Useful Life Wear out Failure Rate al Time