I think C is the answer i.e can be answered uisng both statements.
first one is not sufficient as multiple value of m and n can occur. so one is insufficient .
for the same reason 2 also . multiple value of m and n like 6*5, 5*6, 30*1
both combined can give answer as only one case is true i.e 15*2 we can be sure about that any other thing does not work , like 6*5, 30*1 . any other combination . so answer is c .