Water flows through a tube of $3$ cm internal diameter and length $20$ m. The outside surface of the tube is heated electrically so that it is subjected to uniform heat flux circumferentially and axially. The mean inlet and exit temperatures of the water are $10^\circ C$ and $70^\circ C$ respectively. The mass flow rate of the water is $720 \: kg/h$. Disregard the thermal resistance of the tube wall. The internal heat transfer coefficient is $1697 \: W/m^2 \cdot K$.Take specific heat $C_p$ of water as $4.179 \: kJ/kg \cdot K$. The inner surface temperature at the exit section of the tube is ___________ $^\circ C$ (round off to one decimal place