Answer
(a) disagree
(b) agree
(c) agree
Work Step by Step
(a) We know that the choice of $y=0$ can change the absolute values of the potential energy, hence your answer and your friend's answer will disagree.
(b) We know that the choice of $y=0$ does not have any affect on the change in potential energy, hence your and your friend's answer will agree.
(c) We know that the kinetic energy is determined on the basis of change in potential energy and as the choice of $y=0$ has no effect on the change in potential energy. Thus, your and your friend's answer will agree.
