If the cup of water contained hot water. Sugar will dissolve a lot slower if it was in room temperature and even slower if it was in cold water.
If you are given the
standard potential for the reduction of X^2+ is +0.51 V, and the standard
potential for the reduction of A^2+ is -0.33, just add the two. The standard
potential for an electrochemical cell with the cell is 0.18V