<prompt> Translate the following text to SwahiliUsing cost models to estimate the cost and length of time necessary to develop a new software system, for example, is appropriate only after requirements have been defined, a system design has been developed, and the size of the new system has been estimated.  <response>: Kutumia mifano ya gharama kwa makadirio ya gharama na urefu wa muda unaohitajika kuendeleza mfumo mpya wa programu, kwa mfano, ni sahihi tu baada ya mahitaji yamefafanuliwa, muundo wa mfumo umebuniwa, na ukubwa wa mfumo mpya umekadiriwa. 