Two long, eccentric cylinders having diameters of 20 and 5

Two long, eccentric cylinders having diameters of 20 and 5 cm, respectively, are maintained at 100 and 20ºC and separated by a material with k = 2.5 W/m · ºC. The distance between centers is 5.5 cm. Calculate the heat transfer per unit length between the cylinders.