You have b boxes and n dollars. If I want any amount of money, from zero to n dollars, you must be able to hand me zero to b boxes so that I get exact

You have b boxes and n dollars. If I want any amount of money, from zero to n dollars, you must be able to hand me zero to b boxes so that I get exactly what I request.
divide the amount into powers-of-two sizes: 1 2 4 8 16 32 etc