Incomplete question; lacks options. However, I answered from a general perspective.
Answer:
regret of purchase
Step-by-step explanation:
It is noteworthy that Mieko made a purchase of the photocopier without giving much thought to the action.
Since it appears the new machine lacks a built-in stapler, it seems they may still need to rent staplers, which would thus constute part of the company's cost in the long run.
Hence, Mieko is experiencing a regret of her purchase.