The cost of a single-phase cable is (20000A+2400) per Km where A is the area of the cable in cm2. If the line current is 250 A and it is assumed to be constant throughout the year. The cost of energy is 5 p per kWh. The total interest and depreciation is 10% per year. Find the most economical size of the cable in cm if the specific resistance of the conductor material is 1.73×10^-6 Ωcm.