Air flows through a 10cm diameter tube at Reynolds number 1700 with thermal conductivity of air as 0.2792 W/mK and constant heat flux condition is maintained with a temperature of pipe is 50C above air temp all along the length. The heat transfer per unit length is (a) 12.2 W/m (c) 106.82W/m (b) 24.4W/m (d) 191.6W/m