Value chain analysis is a tool used to:
a. identify the firm's core competencies in each of the primary activities of the firm.
b. analyze a firm's value chain activities and support functions in isolation from its competitors' value chain.
c. understand the parts of the firm's operation that create value and those that do not.
d. analyze a firm's external environment for value-creating opportunities.

c)  understand the parts of the firm's operation that create value and those that do not.

Explanation:

Value chain analysis (VCA) is a process where a firm identifies its primary and support activities that add value to its final product and then analyze these activities to reduce costs or increase differentiation.

Value chain represents the internal activities a firm engages in when transforming inputs into outputs.

Value chain analysis is a strategy tool used to analyze internal firm activities. Its goal is to recognize, which activities are the most valuable (i.e. are the source of cost or differentiation advantage) to the firm and which ones could be improved to provide competitive advantage. In other words, by looking into internal activities, the analysis reveals where a firm’s competitive advantages or disadvantages are. The firm that competes through differentiation advantage will try to perform its activities better than competitors would do. If it competes through cost advantage, it will try to perform internal activities at lower costs than competitors would do. When a company is capable of producing goods at lower costs than the market price or to provide superior products, it earns profits.

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