This is the question in that above questio. Two equations are mentioned. So i will rake screenshot of that too

4.2-1. Mean Thermal Conductivity in a Cylinder. Prove that if the thermal conductivity varies linearly with temperature as in Eq. (4.1-11), the proper mean value k, to use in the cylindrical equation is given by Eq. (4.2-3) as'in a slab. 4.2-2. Heat Removal of a Cooling Coil. A cooling coil of 1.0 ft of 304 stainless-steel tubing having an inside diameter of 0.25 in. and an outside diameter of 0.40 in. is being used to remove heat from a bath. The temperature at the inside surface of the tube is 40F and is 80 F on the outside. The thermal conductivity of 304 stainless steel is a func- tion of temperature: k = 7.75 + 7.78 10-T where k is in btu/h ft F and T is in F. Calculate the heat remosal in btu/s and watts. Ans, 1.225 btu/s. 1292 W