I agree with many of the posts up there. 4 hours of sleep for 4 months will make you go nuts. And why get up that early and go to bed so late anyway if you get off work at 6??
If you want to study 4 hours a day just do it after work, eg from 7 to 11.
You would do about 30 hours per week for 4 months = almost 500 hours? What for? To get a lot of oohs and aahs in the forum?