A 150-lb drunkard falls in a vat of whiskey. Whiskey has SG = 0.92, whereas the drunkard has SG = 0.99. The drunkard, who wants to stay alive long enough to drink his fill of the whiskey, "treads water," keeping his head above the whiskey. If his head up to his mouth is 15% of his body volume, how much upward force must he exert by "treading water" to keep his head out of the whiskey?