Final answer:
The optimal decision for the purchasing agent depends on various factors and without specific details, it is not possible to determine the optimal decision.
Step-by-step explanation:
The optimal decision for the purchasing agent would depend on various factors such as the quality, price, reliability, and delivery times offered by each source. Without knowing these specific details, it is not possible to determine the optimal decision. Hence, the correct answer would be option d) Not enough information to decide.