In this question will the formula of compound be M2N3 or N3M2

1.16 A compound is formed by two elements M and N. The element N
forms ccp and atoms of M occupy 1/3rd of tetrahedral voids. What
is the formula of the compound?

CCP means face-centered and has 4 atoms per unit cell on the lattice points.
No of tetrahedral voids  = 2 *no of atoms = 8
No of N atoms per unit cell = 4
No of M atoms = 8* 1/3 = 8/3
So the formula is    M8/3: N 4
                  M2/3: N
so the formula is M2N3