Answer
a) About 490 megawatts at 6:00 a.m. and 720 megawatts at 6:00 p.m.
b) About 4:00 a.m.
c) About 11:50 a.m.
d) About -100 megawatts
Work Step by Step
a) We find the P(MW) values when t(h) are 6 and 18.
b) The lowest power consumption can be found by finding the lowest point on the graph.
c) The highest power consumption can be found by finding the highest point on the graph.
d) First, we find both values which will be $P(9)\approx 795$ MW and $P(19)\approx 695$ MW, then we subtract the first one from the second one: $P(19)-P(9)=695-795= -100$ megawatts. And that will be the net change.