To calculate the unit price of a product, you divide the total price by the total number of units (in this case, ounces).
For the 28-ounce jar of spaghetti sauce priced at $2.89, the unit price would be calculated as follows:
\[ \text{Unit Price} = \frac{\text{Total Price}}{\text{Total Ounces}} = \frac{2.89}{28} \]
Therefore, none of the provided options (a, b, c, d) directly show the correct calculation for the unit price, as they either multiply, subtract, or are unclear images rather than representing the division needed to find the unit price.
In summary: The correct method for finding the unit price is \( \frac{2.89}{28} \).