public void AddSeries( 
   BaseSeries series,
   SeriesChartType chartType,
   Grouping grouping
)

var c = document.AddChart<ComboChart>();

// Two STACKED Columns (Online + In-Store stack into one Column per category)
c.AddSeries( online,    SeriesChartType.Column_Clustered, Grouping.Stacked );
c.AddSeries( inStore,   SeriesChartType.Column_Clustered, Grouping.Stacked );

// A STANDARD (clustered) Column in the same Chart
c.AddSeries( marketing, SeriesChartType.Column_Clustered, Grouping.Standard );

// A line on top
c.AddSeries( profitLine );