Final answer:
To find the cost per mL of gasoline, convert the volume from liters to milliliters and then divide the cost by the converted volume. The cost per mL is approximately $0.92.
Step-by-step explanation:
To find out how much a mL of gasoline costs, we need to convert the given volume of gasoline from liters to milliliters and then divide the cost by the converted volume.
Since there are 1000 milliliters in a liter, we multiply 22.71 liters by 1000 to get 22710 milliliters.
Next, we divide $21.00 by 22710 to find the cost per mL, which is approximately $0.92.
Therefore, the correct answer is option a) $0.92.