c. Choose a value for d that is greater than $25 and less than $100. Calculate the total cost of each of the possible presents for the value you chose. Then write a short paragraph telling Winona and Takoda which present they should buy and explaining why.
Let's choose d = $60, between $25 and $100.
Total cost for present 1: $12.75 + $60 = $72.75
Total cost for present 2: $20.50 + $60 = $80.50
Total cost for present 3: $9.90 + $60 = $69.90
Based on these calculations, Winona and Takoda should buy present 3, which costs $69.90. This is the most affordable option out of the three presents. Despite having a lower initial cost, present 1 ends up being more expensive due to the additional 15% tax, and present 2 remains the most expensive option overall. By choosing present 3, they can save money while still getting a quality gift for their friend.