3. Store E offers a book that Karen wants for 20% off its regular price of $15.00. Store F sells the same book for $15, before a $3.00 mail-in rebate. Where should Karen purchase the book? Explain your reasoning. (Be sure to consider the cost of postage, as well as the time and effort required to mail in the rebate request in your response.)

To determine where Karen should purchase the book, we need to compare the final prices she would pay at Store E and Store F.

At Store E, the book is offered at a 20% discount, so Karen would pay 80% of the regular price: $15.00 * 0.80 = $12.00.

At Store F, the book is sold for $15.00, but there is also a $3.00 mail-in rebate. This means that Karen would initially pay $15.00 and then later receive a $3.00 rebate, resulting in a final price of $15.00 - $3.00 = $12.00.

So, both Store E and Store F would offer Karen the book at the same final price of $12.00. However, we also need to consider the cost of postage and the effort required to mail in the rebate request.

If the postage cost exceeds $0.00, then it would be more convenient for Karen to purchase the book at Store E where she can immediately enjoy the discounted price, without the hassle of mailing in a rebate request.

Therefore, if the cost of postage is greater than $0.00, Karen should purchase the book from Store E. But if the cost of postage is $0.00 or negligible, then she can choose either Store E or Store F based on her preference.