We are given 1988 unit cubes. Using some or all of these cubes, we form three quadratic boards A,B,C of dimensions a×a×1, b×b×1, and c×c×1 respectively, where a≤b≤c. Now we place board B on board C so that each cube of B is precisely above a cube of C and B does not overlap C. Similarly, we place A on B. This gives us a three-floor tower. What choice of a,b and c gives the maximum number of such three-floor towers? combinatoricscombinatorial geometry