equation for pressure in bottom layer of a 2 layer fluid is: pressure,p =( specific weight of fluid 1,y1*thickness of fluid 1,h1) + ( specific weight of fluid 2,y2 * ( depth below the free surface at which the pressure is being determined, h - thickness of fluid 1,h1) Provide an equation that give an uncertainty of pressure in terms of y1, h1, y2 and h.