Each episode takes 20*.5=<<20*.5=10>>10 minutes longer to film than it is
So it takes 20+10=<<20+10=30>>30 minutes
They are filming 5*4=<<5*4=20>>20 episodes
So it takes 20*30=<<20*30=600>>600 minutes
This is equivalent to 600 / 60 = <<600/60=10>>10 hours
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