A spherical container 20 inches in diameter is filled with water at a temperature of 70 Solution from Energy balance equation We know that ln((Tf-Tb)/(Tf-Ta))=-hAt/pVCp Where Tf=bath oil temp Tb=Final container water temp Ta=initial container water temp V=volume of container A=surface area h=heat transfer coefficient of thewall of the container is= 40,000 Btu/hr ft2.