[填空题]
Energy may be stored :x9 l48okcpq5her)zohl;tiym: wz,.for use during peak demand by pum qb det i5n(ks,bx-p5)ping water to a high reservoir when demand is low and qpe),kd -5n(5 btxbi sthen releasing it to drive turbines when needed. Suppose water is pumped to a lake 135 m above the turbines at a rate of $ 1.00\times10^{ 5}kg/s$ for 10.0 h at night.
(a) How much energy (kWh) is needed to do this each night? $\times10^{9 }W\cdot\,h$
(b) If all this energy is released during a 14-h day, at 75% efficiency, what is the average power output? kW
