$1.$ A computer user ordered an accounting system from a popular software vendor$$s Web site. When he received his order, he found that the store had accidentally sent him a very expensive word$-$processing program as well as the accounting package he had ordered. The invoice listed only the accounting package. The user decided to keep the word$-$processing program.

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a$.$ The customer$$s decision to keep the word$-$processing program was:

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