In certain locales, power transmission is made by means of underground cables. In one example an 8.0-cm-diameter cable is buried at a depth of 1.3 m, and the resistance of the cable is 1.1 × 10−4 Ω/m. The surface temperature of the ground is 25ºC, and k = 1.2 W/m· ºC for earth. Calculate the maximum allowable current if the outside temperature of the cable cannot exceed 110ºC.