A time series {X+} is differenced at lag 12, then at lag 1 to produce a zero-mean series {Y} with the following sample ACF: and (0) parameters. = (12j) (.8), j = 0,1, 2,... (12j1) (.4)(.8), j=0,1, 2, . 0, otherwise 25. Suggest a SARIMA model for {X+} specifying all Q