Problems are rated on the dagger scale below:

$\dagger$

An easy problem that a prepared student should be able to answer with minimal effort.

$\dagger\dagger$

Your standard problem. ``B'' students should be able to solve a reasonable fraction of these problems.

$\dagger\dagger\dagger$

This problem is slightly harder than your average problem. Usually this difficultly is conceptual, not technical. That is, the problem is solvable by the standard techniques. An able practitioner would be able to proceed directly to the answer without taking a wrong turn. ``A'' students should be able to solve a reasonable fraction of these problems.

$\dagger\dagger\dagger\dagger$

This problem is meant to challenge the best students. This problems would probably cause an able practitioner some pause. Often this is because the most obvious approach fails for some reason.