A model for evaluating software designs based on extending the functional model of program verification with concepts from economic decision theory has been proposed. The authors describe the method, and discuss a prototype implementation of a tool, called Selector, which implements this technique. It is suggested that a system like Selector can be used in two ways: as a decision support system for management to be used in the process of making choices among various alternatives; and as a prototyping investigative system for proposing and answering a series of 'what if' scenarios. The proposed model depends on a risk analysis, of each potential solution and aspects of decision theory to modify the evaluation strategy. The model depends on equilibrium probabilities for generating answers.>