what is the total number of electrons that can occupy the 4f orbitals?
The number of electrons in a 4f subshell can be anything between 0 (if it isn't filled) and 14 (2 electrons per orbital times 7 orbitals = 14 electrons). Note that a 4f subshell can also have fewer than 14 electrons, and all f subshells (not just n=4) can hold the same maximum number of electrons.