CEDE
If = 2 then C??E because CODE = 2 and COLD = 1, last letter in known to be E, so COD? =1 and COL? = 1 therefore D/L swop = no change. so if CO?? = 1 and CE?? =1 it must be C???
else
if = 1 then?O?E because CODE = 2 but CEDE = 1, last is know and can't be ??D? as explained above. so CO?? -> CE?? resulted in -1 so it must be ?O??
if = 3 then CE?E because CODE = 2 but CEDE = 3, last is know and can't be ??D? as explained above. so CO?? -> CE?? resulted in +1 so it must be CE??