How many distinct atoms (including the phenoxide oxygen) can carry the negative charge in the resonance forms of the 4-nitrophenoxide ion?

In the phenoxide part the charge is on O, and on ring carbons C2, C6 (ortho) and C4 (para): 4 atoms. At C4, which bears the nitro group, the charge can move on into the nitro group, placing it on the two nitro oxygens. The nitrogen never carries the negative charge. Total = 1 + 3 + 2 = 6 atoms.