[Argorak]

Fixed contracts (Option 4) are extremely problematic for clients. I rarely seen one of those going well.

There are 2 options:

a) The supplier is not an expert in this and will have problems with the project changing scope and maybe running over budget and time which they cannot invoice. This leads to the supplier being at the unfair end of the deal, leading to poor work by the numbers.

b) The supplier is an expert, works on a fixed scope and denies all requests for changes (without renegotiation). This rarely works in favour of the client. I had prospective clients coming back to us after another company wrote them a software perfectly for their spec, but they realized in the middle that the spec was not fitting their business case properly.