d) because nobody knows how much non-trivial project takes until its done. Its well known that developers missestimate time needed by the factor of 4 to 8.

So d) which you miss, is about 4 months. Anything else is not professional and you cut corners. There is no such thing as 2 weeks in enterprise - hello world would take more with adequate docs, ci/cd, metrics, proj. management, optimizations, authorizations etc.