If you could chooses between to nearly identical products the one that is free and the other you have to pay for which would you choose why

well I do have to say nothing is free because someone somewhere has to pay for it but for your example I would choose the free one because I do not have to pay for it and it is identical to the other one so there isn't much difference I would use the money I didn't use for it for something more important

e/c, where e is its total energy

option number c is the right answer.