A welding rod with κ = 30 (Btu/hr)/(ft ⋅ °F) is 20 cm long and has a diameter of 4 mm. The two ends of the rod are held at 500 °
C and 50 °C. (a) In the units of Btu and J, how much heat flows along the rod each second? (b) What is the temperature of the welding rod at its midpoint?