Hello Alaa,

In case like this you have firt of all to clearly state your interviewer that you thought about these costs. Then he will tell you if you have to enter this discussion and deep dive the costs or not. In case you have to do an estimation of the costs, you should name the most common general costs (personnel, raw materials, transportation ecc..). You are not asked to know what are the value of each cost for a particular industry, but it's likely that the interviewer will ask you an estimation and qualitative comments about the costs. (g.e. for a company producing elevators I would say that R&D or marketing are not significant costs).

It often happens that you have to consider the cost part, try to have a clear list of costs in your mind that you can quickly write down.