Triangle ABC is a right angle triangle. The point of circumcentre and the point of orthocentre is the same point, as shown in the diagram below. The coordinate of the point is (2.5, 2.5)
For T = 89.5 degrees C: E(t) = 1100(90 - 89.5) + 520(90 - 89.5)^2= 1100(0.5) + 520(0.5)^2= 550 + 130= 680 m For T = 90 degrees C: E(t) = 1100(90 - 90) + 520(90 - 90)^2= 0 + 0= 0 m (meaning that boiling point is 90 degrees C at ground level)