In a steam power plant, superheated steam at $10$ MPa and $500^\circ C$, is expanded isentropically in a turbine until it becomes a saturated vapour. It is then reheated at constant pressure to $500 ^\circ C$. The steam is next expanded isentropically in another turbine until it reaches the condenser pressure of $20$ kPa, Relevant properties of steam are given in the following two tables. The work done by both the turbines together is _________ kJ/kg (round off to the nearest integer).
Superheated Stream Table:
$\begin{array}{|c|c|c|c|} \hline \text{Pressure,}p & \text{Temperature}, T & \text{Enthalpy}, h & \text{Entropy}, s \\ \text{MPa} & (^\circ C) & (\text{kJ/kg}) & \text{(kJ/kg.K)} \\ \hline 10 & 500& 3373.6 & 6.5965 \\ \hline 1 & 500 & 3478.4 & 7.7621 \\ \hline \end{array}$
