It will likely be different, depending on which program you're using. There may be better programs, (I use Irfanview, a non-commercial Freeware program http://www.irfanview.com/ ), but Windows Paint should also do the job.
Open the image in paint, then go to Image>Stretch/Skew then reduce horizontal and vertical by the same percentages to decrease the file size to what you desire. Then save the .tif file as a .jpg.
Although I haven't actually tried it on these files, I have done similar with other images.