To find the unit price for each option, we need to divide the total price by the number of ounces.
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48 ounces for $4.50: \[ \text{Unit Price} = \frac{4.50}{48} \approx 0.09375 \text{ dollars per ounce} \]
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64 ounces for $3: \[ \text{Unit Price} = \frac{3}{64} \approx 0.046875 \text{ dollars per ounce} \]
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128 ounces for $7: \[ \text{Unit Price} = \frac{7}{128} \approx 0.0546875 \text{ dollars per ounce} \]
Now let's compare the unit prices:
- 48 ounces: $0.09375 per ounce
- 64 ounces: $0.046875 per ounce
- 128 ounces: $0.0546875 per ounce
The 64-ounce option has the lowest unit price of approximately $0.04688 per ounce.
Therefore, the answer is:
64 ounces.