Answer the following questions:-(Software engineering questions on SDLC models)

i)Suppose a travel agency needs a software for automating its book keeping activities.The set of activities to be automated are rather simple and are at present being carried out manually.The travel agency has indicated that it is unsure about the type of user inteface which would be suitable for its employees and its customers.Would it be proper for a development team to use the spiral model for developing the software?

ii)Assume that a software development company is already experienced in developing payroll software and has developed similar software for several customers(organizations).Assume that a software development company has received a request for a certain customer (organization) which was still using manually processing of the payrolls.For developing the payroll software for this organization which life cycle model should be used.Justify