c$.($Sender authentication with cheating third party$)$ Oscar claims that he sent some message x with a valid auth$($x$)$ to Bob but Alice claims the same. Can Bob clear the question in either case?

d$.($Authentication with Bob cheating$)$ Bob claims that he received a message x with a valid signature auth$($x$)$ from Alice $($e$.$g$.,$Transfer $$1000$ from Alice to Bob$)$ but Alice claims she has never sent it$.$ Can Alice clear this question in either case?