Final answer:
The domain of the function f(g) = 3.50g, representing the cost of gas in relation to gallons, for a car that holds up to 12 gallons, is [0, 12].
Step-by-step explanation:
The most appropriate domain of the function f(g) = 3.50g, which models the relationship between the total cost of gas and the number of gallons of gas purchased, is the range of values that g, the number of gallons, can take. Since Sarah's car holds a maximum of 12 gallons of gas, the domain for g would be all real numbers that are greater than or equal to 0 and less than or equal to 12. This is because Sarah cannot purchase a negative amount of gas, she can fill her car with any amount of gas up to 12 gallons, but not more. Hence, the domain is [0, 12].