A manager is reviewing the firm's market data and learns that it is losing its competitive advantage on a product that was designed and released in the market one year ago, though several other products released in years past maintained its competitive advantage for years. Which lesson does this underscore for savvy managers? a. Managers need to build firm strengths based on the VRIO framework. b. Relentless imitation is not likely to be a successful strategy. c. Managers need to make sure their jobs cannot be easily outsourced. d. Competitive advantage has become shorter in duration