public class MP4VideoFormat : VideoFormatBase 

//Note: Call within QueuedTask.Run()
await QueuedTask.Run(() =>
{
  //Create mp4 format with appropriate settings
  MP4VideoFormat mp4Format = new MP4VideoFormat();
  mp4Format.Width = 800;
  mp4Format.Height = 600;
  mp4Format.OutputFileName = @"my folder\presentation.mp4";

  //Define Export Options
  PresentationExportOptions options = new PresentationExportOptions
  {
    PageRangeOption = ExportPageOptions.ExportByPageRange,
    CustomPages = "1,2,8"
  };

  //export as mp4
  presentation.Export(mp4Format, options);
});