To find the unit rate price per ounce, you can divide the total price of the bottle by the number of ounces it contains.
The total price of the 64 oz. bottle is $3.20.
So, the unit price per ounce is calculated as follows:
\[ \text{Unit Price} = \frac{\text{Total Price}}{\text{Total Ounces}} = \frac{3.20}{64} \]
Now you can calculate:
\[ \frac{3.20}{64} = 0.05 \]
Thus, the unit rate price per ounce is $0.05.
The correct answer is B: $0.05.