For the function showing the cost in dollars of a sundae weighed in ounces, the domain refers to the input values of the function. For this function, the input value is the weight of the sundae in ounces, because its the weight measured that would determine the output which is the cost of the sundae.
We already know that the weight in ounces can only be measured as positive values. Also, the weight in ounces can be expressed as integers.
Hence for this particular function, the domain, that is, the weight in ounces would be positive integers.
ANSWER:
An appropriate domain would be non-negative integers