If vince charged $200 on his credit card with 18% apr and he paid his balance in full within the grace period, how much is the finance change?

Helen tells her nephew, bernard, that she will pay him $100 if he will stop smoking for six months. helen was hopeful that if bernard stopped smoking for six months, he would stop altogether. bernard stops smoking for six months but then resumes his smoking. helen will not pay him. she says that the type of promise she made cannot constitute a binding contract and that, furthermore, it was at least implied that he would stop smoking for good. can bernard legally collect $100 from helen