P$3\mathrm{.}16$ The difference in elevation between the levels upper and lower reservoirs of a pumped hydro plant is a constant $100$ m $.$ Assuming that the roundtrip efficiency of the plant is $\backslash (75\backslash \%\backslash ),$ calculate the power it would re$-$inject in the system after pumping $\backslash (4,000,000\backslash$mathrm$\{$~m$\}^\{3\}\backslash )$ if this water were released at a constant rate over four hours.

P$3\mathrm{.}17$ The owner of a $10$ MW$/80$ MWh battery energy storage system has paid $\backslash (\backslash$$ $640\backslash )$ to raise its state of charge from $\backslash (10\backslash \%\backslash )$ to $\backslash (90\backslash \%\backslash ).$ At what price $(\backslash (\backslash$$ $/\backslash$mathrm$\{$MWh$\}\backslash ))$ should it sell this energy back to break even? Assume that the roundtrip efficiency of the storage system is $\backslash (80\backslash \%\backslash ).$

P$3\mathrm{.}18$ What policy decisions have influenced or are currently influencing the choice of generation technologies in your region?