Good job! The major compound in both A and B will be maleic acid.

Referring back to the experimental procedure, once all of maleic anhydride is converted to maleic acid the hot solution is passed through a gravity filtration system. The hot filtration severs to remove impurities within the solution.

All of the maleic acid is containing within the flowthrough. It's important to known that at this stage of the procedure you have a super saturated solution of maleic acid. Thus, as the solution cools down some of maleic acids crystalizes out of solution. The crystallized maleic acid is now collected by suction filtration and dried out. The remaining maleic acid is found still in the filtrate and will serve as the precursor for the isomerization of maleic acid to fumaric acid.