150 kbps video + 32 kbps audio = 182 kbps total. For a 90 minute film (5400 seconds): 182 * 5400 / 8 = ~122MB. Adjust bitrate down to 120kbps to hit 100MB exactly.
The bitrate is often pushed down to under 200 kbps , whereas a standard HD stream uses 3,000–6,000 kbps [10]. Highly Compressed Movies Under 100mb