Consider a phase cycle in which the pulse phase goes through the three steps [0, 120, 240

Question:

Consider a phase cycle in which the pulse phase goes through the three steps [0°, 120°, 240° ]. Devise a set of accompanying receiver phase shifts (which will not be multiples of 90°) which will select a pathway with Δp = -2. Without further detailed calculations, explain which other values of Δp will be selected or rejected by this three-step sequence.
Explain how this three-step sequence could be used to select the appropriate pathway for N-type COSY, and devise another three-step cycle to select the pathway for P-type COSY.