Let's choose a value for \( d \) of \( 50 \) (which is greater than \( 25 \) and less than \( 100 \)).
Assuming the possible presents along with their individual costs are as follows:
- Present A: $30
- Present B: $40
- Present C: $20
- Present D: $60
Now, we need to calculate the total cost of each present when the value of \( d \) is added to them:
- Present A: \( 30 + 50 = 80 \)
- Present B: \( 40 + 50 = 90 \)
- Present C: \( 20 + 50 = 70 \)
- Present D: \( 60 + 50 = 110 \)
Next, we notice that Present D exceeds our budget when combined with \( d \). Now, let’s summarize the total costs of the viable presents:
- Total cost of Present A: $80
- Total cost of Present B: $90
- Total cost of Present C: $70
Based on their total costs, I would recommend Winona and Takoda to buy Present C, which costs $70 when \( d \) is added. It provides the best value since it's the least expensive option within their budget, allowing for a potential savings that could be used for additional items or experiences.