$2\mathrm{.}45.$ A $150-lb$ drunkard falls in a vat of whiskey. Whiskey has $SG=0\mathrm{.}92,$ whereas the drunkard has $SG=0\mathrm{.}99.$ 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?