slides 1-3,9-11,13,14,20,21,23,25-27 (wich is exacly half) are all about 10-15 seconds long
The rest is marginally longer (30seconds with very few slides around a minute)
I could easily cut about 8 slides: 3, 8, (7 or 9), 11, 18, 20, 21, 27 this is about two minutes max. This could however...