Andrew should create shelves that hold 24 cd's each. This will accomplish two things - first, he will only need five shelves, which will take up limited space and distribute the weight load evenly on his wall. Secondly, while there will be 2 shelves of country cd's and 3 shelves of rock cd's,, there will not be an excessive amount on any one shelf, and he'll be able to find the cd he is looking for rather quickly.