I’m pretty sure it’s the third option, Bella saves more per chore than Sweet T. If you replace the c in Bella’s equation with 1, it would be 3.5 times 1 which is 3.5 and then add 11 and it would be 14.5 which is more then Sweet T. You can do this with the rest of the numbers and Bella would still have more then Sweet T. Per chore