It is really necessary for service firms to engage in research and development? in planning for production and operations control?

Yes just because they are a service firm does not mean they should slack in the area. This area is directed toward innovation, introduction, and improvements of products. There are many things that can be learned through this area regardless if people think they know everything in their field. There are still lot of things to learn like product research and development. It goes hand in hand with market research and development. Considerable connection is required between these two areas, and procedures need to be standardized. Setting up a production process or a new line can involve considerable cost, and careful work in the early stages will help to ensure that profits are made. Product researchers use marketing data to help them to develop products or services and choose suitable designs.

answer: marginal utility of the fourth brownie is 0.

explanation: marginal utility is the addtional utility gained from the consumption of one more unit of a good. it is given by,

so, marginal utility at the 4th unit will be given by

since, the values are not given here, you can simply find marginal utility at fourth unit by subtracting total utility at 3rd unit from total utility at 4th unit.