Answer
The domain can be b$\geq$0
The range can be C$\gt$0
Work Step by Step
The domain for this relation has to be b$\geq$0 because the manager can buy 0 bags or she can buy as many bags. However she can't buy negative bags so it can be 0 or more.
The range for this relation has to be C$\gt$0 because the cost per bag can't be 0, so the price per bag can be very close to 0 dollars but never be 0.