The economics of component parts selection

It is often said that the best buy is not necessarily the lowest cost article which can be purchased. It is usually the article which will perform the required function for the required time with minimum over-all cost. Equipment may be designed to meet one or intermediate grades of the following requirements: 1. Lowest manufacturing cost (where maintenance costs are unimportant). 2. Minimum total cost (consisting of manufacturing, installation, and maintenance costs for the required time the equipment is to be used). 3. A minimum number of failures for the required time. (No compromises are to be made in manufacturing, installation, and preventive maintenance to achieve this goal.)