The incremental costs (in Rupees/MWh) of operating two generating units are functions of their respective powers $P_{1}$ and $P_{2}$ in $MW$, and are given by
$\dfrac{dC_{1}}{dP_{1}}=0.2P_{1}+50$
$\dfrac{dC_{2}}{dP_{2}}=0.24P_{2}+40$
where
$20MW \leq P_{1} \leq 150MW$
$20MW \leq P_{2} \leq 150MW$
For a certain load demand, $P_{1}$ and $P_{2}$ have been chosen such that $dC_{1}/dP_{1} = 76$ Rs/MWh and $dC_{2}/dP_{2} = 68.8$ Rs/MWh. If the generations are rescheduled to minimize the total cost, then $P_{2}$ is ________.