I'm not sure...
I feel ya.
From Carnot's theorem, for any engine working between these two temperatures:
efficiency <= (1-tc/th) * 100
Given: tc = 300k (from question assuming it is not 5300 as it seems)
For a, th = 900k, efficiency = (1-300/900) = 70%
For b, th = 500k, efficiency = (1-300/500) = 40%
For c, th = 375k, efficiency = (1-300/375) = 20%
Hence in case of a and b, efficiency claimed is lesser than efficiency calculated, which is valid case and in case of c, however efficiency claimed is greater which is invalid.
Draw a right triangle so that its hypotenuse is 600 ft. The adjacent side is below the vertical, and it makes an angle of 75° with the hypotenuse.
Let h = height of the right triangle.
By definition,
sin75° = h/600
h = 600*sin75° = 579.555 = 580 ft (nearest ft)
Answer: 580 ft (nearest foot)
