Methods of Project Appraisal

So I have gotten this topic right and I am able to calculate NPV, Payback and IRR on a given set of Cashflows. I am however stuck on how to tackle the section B of the mock exam questions on the topic. Given the initial cost, scrap value, number of years.... and then expected revenue and costs during the project's lifespan, how does one calculate the NPV, and subsequently payback? essentially, how is the yearly cashflows determined. Mr John Moffat Is there a reason there are no workings to the section B answers of the mock exams?:-( as is the case with section A? (",)