Number of positive integral solutions of the equation XYZ=90 is equal to?

90=2*3*3*5 . So by using permutation and combination , answer=3c1*3c2*3c1(for factors). Also it is possible when all 3 I.e. xyz are positive or 2 of them are negative. Hence for that multiply ans by 2c1.Final answer : 3*3*3*2=54