To find the total cost for 7 granola bars and 9 bottles of water, we will first calculate the unit prices for both the granola bars and the bottles of water.
Step 1: Calculate the unit price for granola bars.
The price for 6 granola bars is $7.14. \[ \text{Unit Price for Granola Bars} = \frac{7.14}{6} \approx 1.19 \text{ (rounded to two decimal places)} \]
Step 2: Calculate the cost for 7 granola bars.
Cost for 7 granola bars: \[ \text{Cost for 7 Granola Bars} = 7 \times 1.19 \approx 8.33 \]
Step 3: Calculate the unit price for bottles of water.
The price for 8 bottles of water is $8.72. \[ \text{Unit Price for Water Bottles} = \frac{8.72}{8} \approx 1.09 \text{ (rounded to two decimal places)} \]
Step 4: Calculate the cost for 9 bottles of water.
Cost for 9 bottles of water: \[ \text{Cost for 9 Water Bottles} = 9 \times 1.09 \approx 9.81 \]
Step 5: Calculate the total cost.
Total cost: \[ \text{Total Cost} = 8.33 + 9.81 \approx 18.14 \]
Therefore, the answer is a. $18.14.
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