Steam at 260 C flows inside a steel pipe (k= 61 W/m.K) whose internal and external diameters measure 10 and 12 cm respectively, in an environment with a temperature of 20 C. The heat transfer coefficients inside and outside the pipe are 120 W/m2.K and 14 W/m2.K, respectively. Determine how thick the insulation must be (K= 0.038 W/m.k) to reduce heat loss by 85%.