I am also not sure but what made me choose incremental is that the question clearly mentioned the fact the portfolio contained only 1 position and that one new position was about to be added. Maybe I am wrong but I would use MVaR in case we want to increase the exposure to particular asset and not add a new one which is currently not in the portfolio.MVaR is linear approximation (first partial derivative). Incremental VaR is a full revaluation.
Not sure which one to use as both will give the similar result. However MVaR will be a very fast way to derive so I chose MVAR.