About how many hours do an electrician and a plumber spend installing things into a brand new house?

I'm writing an essay over Habitat for Humanity, and so I'm wondering how much money a plumber and an electrician miss out on if they volunteer to install everything with no charge...I have their average pay per hour, I just need the hours! A typical Habitat house is anywhere from 1000-1300 square feet, three bedrooms, and two bathrooms. (single story)