Decide which of the unknown quantities are the target variables. check all that apply. view available hint(s) check all that apply. u′: the final gravitational potential energy xmax: the maximum compression of the spring δuint: the change in the internal energy of the package and incline fs: the static friction force δd: how close the package is to its original position fk: the kinetic friction force n: the normal force d′: the final position of the package