Answer
(a) $500 MW$, $730MW$
(b) $4 AM (04:00), Noon(12:00), Yes.$
Work Step by Step
(a) The power consumption at 6 AM (06:00) was $\bf\text{500 megawatts}$.
The power consumption at 6 PM (18:00) was $\bf\text{730 megawatts}$.
(b) The power consumption was the lowest at 4 AM (04:00), and the highest at Noon(12:00).
This seems reasonable because in the middle of the day, most people are active and using power, but in the very early morning most people are asleep and using little power.
