How many moles of ncl3 contain 2.55 × 1024 chlorine atoms?

When we have Cl atoms = 2.55 x 10^24 in NCl3

so,
1-  we need first to get moles of Cl = atoms / Avogadro's number

                                                          = 2.55x10^24 / 6.022 x 10^23

                                                          = 4.23 moles

2- and when NCl3 contains 3 Cl atoms :

so moles of NCl3 = moles Cl / 3 

                              = 4.23 / 3 

                              = 1.41 moles

Idk the answer sorry

The teacher is mostly talking about the distillation of a mixture